TRANSPORT RESEARCH LABORATORY

Toll enforcement using numberplates

Prepared for Tolling and Private Finance Division, Departmentof the Environment, Transport and the Regions

G Gaunt and A Stevens

TRL REPORT 354

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First Published on CD 1998Republished in this format 1999ISSN 0968-4107

Copyright Transport Research Laboratory 1998.

This report has been produced by the Transport ResearchLaboratory, under/as part of a Contract placed by the Departmentof the Environment, Transport and the Regions. Any viewsexpressed are not necessarily those of the Department.

TRL is committed to optimising energy efficiency, reducingwaste and promoting recycling and re-use. In support of theseenvironmental goals, this report has been printed on recycledpaper, comprising 100% post-consumer waste, manufacturedusing a TCF (totally chlorine free) process.

CONTENTS

Page

Executive Summary 1

1 Introduction 3

2 Legal issues 3

2.1 Home Office type approval for traffic enforcement equipment 3

2.2 Use of imaging equipment 3

2.3 Home Office guidance on electronic imaging systems 4

2.4 Criminal and civil offences 4

2.5 Current European practices in key legal areas of enforcement 4

2.5.1 Evidence necessary for enforcement 4

2.5.2 Responsibility for the car 4

2.5.3 Front and/or rear licence plates 4

2.5.4 Photographs of drivers 4

2.5.5 Transmission and storage of images 4

2.6 Process for tracing registered keeper 5

3 Example uses of vehicle registration marks for enforcement 5

3.1 M25 Mandatory variable speed signs 5

3.2 Speed Violation Detection Deterrent (SVDD) 5

3.3 Bus lane enforcement in London 5

4 Automatic Numberplate Recognition (ANPR) systems 6

4.1 Introduction 6

4.2 Analysis of Automatic Numberplate Recognition (ANPR)system errors 6

4.2.1 Methodology 7

4.2.2 Results 7

4.2.3 Discussion of results 8

5 Electronic licence plate 9

5.1 Introduction 9

5.2 Electronic licence plates : a literature review 9

5.2.1 HELP program, CRESCENT demonstrationproject and PrePass 10

5.2.2 Electronic Road Pricing (ERP) project, Hong Kong 10

6 Summary and conclusions 11

7 References 12

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iv

Appendix A: Standards for the display of vehicleregistration marks 13

Appendix B: Vehicle registration mark formats in usein the United Kingdom 15

Appendix C: Tabulated results from the analysis ofautomatic numberplate recognition system errors 17

Appendix D Processing paths for parking tickets andfixed penalty notices 22

Abstract 24

1

Executive Summary

Enforcement of payment is a key issue for the successfuloperation of a UK motorway tolling system and, for asystem without physical barriers, the first stage ofenforcement requires identification of violators. At present,it is anticipated that this will be undertaken by visibleidentification of violator vehicles and the tracing of theperson responsible through the vehicle registration mark.

This report surveys vehicle registration marks andsummarises some of the legal issues surrounding thecapture and transmission of video images for enforcementpurposes based on recent developments of speed and redlight cameras.

The performance of a number of commercially availableautomatic numberplate reading systems is then examinedand their role in the enforcement process discussed.

Since neither visible identification of numberplates nortracing of the responsible person is guaranteed, onepromising alternative identification method is examined.This is based on a ‘tag’ or ‘Electronic Licence Plate’ (ELP)which is permanently affixed to the vehicle.

Numberplates, scanned either visibly or electronically,remain the only practical means of identifying motorwaytoll violators. This report summarises the ‘state-of-the-art’and demonstrates that 100% enforcement is not currentlyachievable for a range of technical reasons (as well aslegal, institutional and commercial ones). It is thereforeproposed that technical investigations and evaluations areundertaken on both video-based systems and electroniclicence plates to better understand their role inenforcement.

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1 Introduction

Enforcement of payment is a key issue for the successfuloperation of a UK motorway tolling system and, for asystem without physical barriers, the first stage ofenforcement requires identification of violators. At present,it is anticipated that this will be undertaken by visibleidentification of violator vehicles and the tracing of theperson responsible through the vehicle registration mark.

This report surveys vehicle registration marks andsummarises some of the legal issues surrounding thecapture and transmission of video images for enforcementpurposes based on recent developments of speed and redlight cameras.

The performance of a number of commercially availableautomatic numberplate reading systems is then examinedand their role in the enforcement process discussed.

Since neither visible identification of numberplates nortracing of the responsible person is guaranteed, onepromising alternative identification method is examined.This is based on a ‘tag’ or ‘Electronic Licence Plate’ (ELP)which is permanently affixed to the vehicle.

2 Legal issues

2.1 Home Office type approval for traffic enforcementequipment

The Home Office approval process has been described byLewis (1996a). Most equipment used for traffic lawenforcement is required to be of a type approved by theSecretary of State under provisions of the Road Traffic Act1991. In the process of obtaining ‘type approval’,equipment is first considered by the Traffic TechnologySub-Committee of the Association of Chief Police Officers(ACPO) Traffic Committee. If, after operationalassessment, the Sub-Committee recommends theequipment to be considered for type approval, it issubjected to technical tests carried out by an approvedindependent test house. These tests are specified inhandbooks published by the Police Scientific DevelopmentBranch (PSDB) of the Home Office. PSDB consider thetest results and make recommendations to the relevantpolicy unit of the Home Office which in turn makesrecommendations to the Secretary of State.

For automatic equipment, the Home Office requires adevice to have an independent means of checking that ithas operated correctly. This is known as the ‘secondarycheck’. It is normally achieved by recording two images,at a known time interval apart, so that the movement of thevehicle between frames can be observed and measuredagainst distance markers on the carriageway. Othermethods may also be used. It is a requirement that it mustbe possible to identify in the image the offending vehicle,its location and any possible extenuating circumstances.The vehicle registration plate must, therefore, be clearlyvisible and a reasonably wide-angle view taken. Textualdata, i.e. the output of the device, the time, date andlocation information are optically introduced into theimage to be included in the photographic record which then

contains all the primary evidence of the offence. The accuracyof the time information can be particularly important wherecameras may operate in close proximity to each other. Clockssynchronised from the time codes broadcast from Rugby, the‘Rugby clock’, are now being used.

Automatic red light and speed cameras have since 1988and 1992 respectively been used by the police to obtainprimary evidence of traffic offences. These use ‘wet film’technology, and include a magazine of film capable oftaking 800 35-mm colour photographs. Disadvantages ofthis approach include the need to periodically change themagazines by physical access to the cabinets and the needto process films and issue penalty notices within aspecified time of the offence.

2.2 Use of imaging equipment

Enforcement of toll violation offences is likely to involvethe use of video cameras taking images of vehiclenumberplates. Extending practice from ‘wet-film’ systemssuch as red light and speed cameras (including the M25mandatory limit cameras) to video cameras raises specificadditional questions which are now being addressed. Themain issues arises from the digital pixel nature of videoimages which render them amenable to manipulation,compression and transmission.

For a digital image to approach the same resolution asthat provided by a 35mm film, approximately 2000 x 2000separate imaging elements would be required.Economically, this is unlikely to be justifiable for anumber of years, so images at multiple resolution have tobe considered.

Image compression is necessary for practical and costreasons. Equipment is already available which is capable ofcompressing and decompressing video-images inapproximately 40 milliseconds, with compression ratios of 4:1.This is fast enough for ‘real-time’ applications. However,the amount of data is still large (about 64K bytes perimage). More sophisticated techniques under investigation,using fractal geometry and other mathematical techniques,promise to provide very high compression ratios with verylittle degradation in image-quality. These techniques maywell prove useful for the transmission and storage of wide-angle shots (if required) but images of licence-platessubject to these processes may not be acceptable in lawunless forensic continuity can be guaranteed. In this casedata-compression may be achieved by retaining either justthe licence-plate image from the (narrow-angle) picture(giving a file of approximately 2K bytes in size) or readingthe licence-plate characters (resulting in a fileapproximately 7 bytes in size). Some questions must beraised about the storage of video images as compressedimages may be considered, in some cases, not an originalpiece of evidence but rather something altered - forensicscience may well be needed to prove whether this is thecase or not (possibly on a case by case basis). The CrownProsecution Service have advised that the appropriate testis a ‘common sense’ one, i.e. a level of compression isacceptable if the image quality remains one for which mostreasonable people would say had clearly portrayed all theinformation relevant to proving the offence.

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2.3 Home Office guidance on electronic imagingsystems

Home Office and ACPO Traffic guidance to industry onrequirements for future traffic enforcement systems, whichinclude the use of electronic imaging, has recently beenpublished (Lewis, 1996b). It requires the evidential data tobe stored at the roadside using WORM (Write Once ReadMany times) technology to provide a physical record.WORM technology is a digital storage medium whichprovides a physical record of the data, but once written,cannot be amended with new data. The image data may becompressed to between 20 and 25 to 1 before being stored.The use of JPEG is recommended.

If the data is to be transmitted over a public data network,then the data must be protected using standard data securitymeasures, of the kind used by the financial institutions,before being stored. A Message Authentication Code(MAC) is computed across the image and text data producedby the enforcement camera. The data is then encrypted andstored with its MAC on the WORM. This is the primaryevidence of the offence. A copy of the stored evidence maythen be transmitted using standard CRC (CyclicRedundancy Check) error checks. At the receiving end theauthenticity of the copy received is determined bydecrypting the evidence data, computing its MAC andcomparing it to the transmitted MAC. The copy may then beused for immediate processing of the evidence.

The equivalent of several months of data will be stored onthe WORM so less frequent visits to the roadside site wouldnormally be required than with wet film systems. However,the primary evidence could still be collected wheneverrequired, for example, because of a legal challenge.

The adequacy of the above measures will remainunknown until tested in the courts.

2.4 Criminal and civil offences

The Home Office type approval procedures outlined aboveapply for the enforcement of traffic offences deemed to be‘criminal’. Traffic offences are criminal by virtue of beingdealt with by the criminal courts. If the collection ofunpaid toll revenue is deemed a civil offence, as seemslikely, then the formal processes would not appear toapply. Arguably, the introduction of decriminalisedparking enforcement has introduced a much more effectivemethod of resolving disputes and of collecting penalties.

Whilst police officers have a clear responsibility in the caseof safety related regulations, as the need for traffic regulationsto be enforced for non-safety purposes grows, allocatingscarce resources will become an increasing problem.

2.5 Current European practices in key legal areas ofenforcement

The following results are based on a questionnaire onvehicle enforcement practices carried out in the AREA 1Forum of DRIVE2, as reported by Blythe (1996). Theresults covered the following countries:

l Finland

l France

l Germany

l Greece

l Ireland

l Italy

l Netherlands

l Norway

l Spain

l United Kingdom

2.5.1 Evidence necessary for enforcement‘Only photographs’ are used by the majority of countries(50%). Photographs in addition to video images are used asenforcement evidence by 20% of the countries as storage mediaand 20% are using digital images in addition to photographsand video. In general, photographs are used by 80% of thecountries followed by video images (40%) and finally digitalimages counted for 20% of the countries involved.

2.5.2 Responsibility for the carConcerning who is responsible for the car in case of violation,there are different practices in the countries involved in thequestionnaire. For example, in Finland, France and Norway,the driver is the responsible person in case of traffic violation,whereas in Ireland, Italy, Netherlands, Spain and the UK thevehicle owner is responsible for the records of his vehicle. InGermany and Greece the responsible party depends on thetype of violation (such as speed limits, parking, toll payment,etc.). In general, the results showed that in 58% of countriesinvolved, the vehicle owner is the responsible person in casesof law violation.

2.5.3 Front and/or rear licence platesSome countries record the front licence plate, some othercountries the rear only, and in some countries both licenceplates are required for legal issues. For example, in France,Germany and Norway the front licence plate is recorded,whereas in Italy and Netherlands the back licence plate canbe used as evidence. In Spain both licence plates arerecorded in case of violation.

2.5.4 Photographs of driversConcerning the privacy of the driver, the enforcementevidence includes the driver as well in case of violation incountries such as Finland, Germany, Netherlands andNorway. In other countries such as France, Greece,Ireland, Italy and Spain the driver is not photographed.

2.5.5 Transmission and storage of imagesThere are different procedures in handling, transmittingand storage of the images of non-compliant vehicles in thecountries involved in the questionnaire. In Germany, forexample, the violation images are saved for a period of 2to 5 years and there is a code of criminal procedure andlegal protection of the individual concerning the use andstorage of computerised data. In Norway, the images aresaved until the fine is paid and there are no rules formovement and transmission of images.

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2.6 Process for tracing registered keeper

One of the major problems in pursuing enforcement of parkingpenalties is the accuracy of keeper information supplied by theDVLA. There are a number of reasons for this:

l Information is out of date because people buyingvehicles, particularly second-hand, are slow inregistering them in a new name.

l Vehicles are not registered by the keeper at all

l Vehicles use false or ‘ringed’ registrations

DVLA is currently proposing that when vehicles changehands, both seller and purchaser must jointly notify DVLAof the transaction. In effect, the proposal transfers theresponsibility for re-registering a vehicle on change ofownership from the purchaser to the seller and the sellerwould be under an obligation to take specified steps toestablish the true identity of the purchaser.

Appendix D contains flow diagrams illustrating theprocessing paths for parking tickets and fixed penalty notices.

3 Example uses of vehicle registrationmarks for enforcement

3.1 M25 Mandatory variable speed signs

The enforcement system (Harbord and Jones, 1996)consists of radar speed measuring equipment, flash and a35mm ‘wet film’ camera to record the identity ofoffending vehicles, a ‘Rugby’ clock receiver to provideaccurate time and a CMII (CMI Interface) to determine thecurrent speed limit displayed to drivers. Conventional filmtechnology and radar based speed detection were adoptedfor the pilot as they provided the only method proven tomeet the requirements of the Home Office SpeedmeterHandbook. A removable memory card, within the CMII,provides a record of offence and operational data to assistwith film analysis, but all essential prosecution evidence iscontained on the 35 mm film, including a record of eachspeed limit change. Status indicators are provided on theCMII and radar to assist in setup and maintenance. Eachoffence photograph includes details of the time, date,location and speed of the offending vehicle as well asindependent indications of the speed limit in force asconfirmed by the primary (electrical) and secondary(optical) interfaces. Two photographs are taken for eachoffence, separated by 0.5 sec, the distance travelledbetween the two photographs providing the secondarymethod of speed measurement required by the HomeOffice’s Speedmeter Handbook. An adjustable delay isintroduced by the system between any change in speedlimit and the start of enforcement, to allow drivers tosafely change their speed. As with existing road-side speedenforcement equipment the offence threshold applicablefor each speed limit can be varied and is determined, inaccordance with agreed ACPO guidelines, by the Policeoperating units.

The enforcement system was specified to meet the relevantrequirements of the Speedmeter Handbook, includingadditional requirements defined by the PSDB to cover the

novel features of the M25 enforcement system. Theenforcement system and the CMIs were subjected to the fullrange of environmental and EMC tests specified by the HomeOffice, in addition to the DOT/HA (now DETR/HA) testsrequired for all motorway equipment. The system wassubjected to extensive tests witnessed by the Police, ACPOand the PSDB.

3.2 Speed Violation Detection Deterrent (SVDD)

SVDD is a system for automatically measuring vehiclespeed and displaying the speed and the vehicle’sregistration mark to the driver. It is the first videoenforcement technique to be processed for Home OfficeType Approval and required development of a new testingstandard encompassing video based technologies (asdescribed above)

The Police Scientific Development Branch (PSDB) wererequested to update the ‘Speed Meter Handbook’ toincorporate the necessary procedures for this and othervideo enforcement systems to ultimately be used by thePolice Service. Discussions between PSDB and SymondsTravers Morgan were held to evaluate the currentoperational requirements set by an ACPO sub-committeeand the future developments of this type of technology.Topics discussed at length encompassed:

a the use of ready-made professional equipment such ascameras, industrial computer components and hardwarepackages

b the generation method of the enforcement data, theaccuracy of the measurements and the system checks forvalidity

c the compilation method of the Violation Record, its datacontent, its vehicle image information and overall layoutfor clarity in a UK court of law

d the traceability of the Violation Record data.

The outcome of these discussions and the guidance given bythe ACPO sub-committee resulted in the PSDB publication ofthe ‘Automatic Distance/Time Speedmeter Handbook’.

These guidelines provided the necessary framework tocommence the testing of the SVDD system. Theprocedures included the appointment of an independentBSI approved Test House to undertake laboratory testingof the system under temperature and humidity togetherwith electromagnetic compliance. Performance testing ofthe complete system was also necessary at an outdoor testtrack. During the planning and implementation of thetesting process extensive consultation was necessary withPSDB and the independent assessor to determine a fair,comprehensive and accurate method of testing noting allthe different configurations and operational parametersthat could be executed with SVDD.

Final testing is expected to take place in 1997, afterwhich the system can be used to enforce speed limitsrather than just warning drivers.

3.3 Bus lane enforcement in London

This scheme, under development by the Traffic Directorfor London, aims to enforce the correct use of bus lanes by

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recording the numberplates and prosecuting offendersusing roadside and bus mounted video cameras.Contravening a bus lane is a complex offence and not onethat can be measured with few qualifications. Following asuccessful demonstration phase, the main scheme will beoperating in 1997.

The demonstration bus-mounted camera system consistedof two colour cameras recording simultaneously onto videotape. One camera recorded any offences and the scene infront of the bus, while the other recorded close-ups of theregistration numbers of vehicles in the bus lane.

The camera system captures the pictures and essentialdata that may be presented in court as admissible evidence.The technology involves recording of electronic images(including those from digital cameras) to computer disk,similar to the next generation of speed and red lightcameras currently under consideration.

To allow the recorded evidence to be admissible incourt, bus lane and bus-only route-offences are to be addedto section 20(2) of the Road Traffic Offenders Act 1998 bythe Home Secretary. Devices that record such evidenceneed to be type-approved, to give the courts and the publicconfidence. PSDB have issued The Bus Lane EnforcementCamera Handbook (Lewis, 1996c) which providesguidance on the type-approval procedures andrequirements. The pictorial evidence will need to showclearly :

l the offence being committed

l the context in which the offence took place

l any possible defences

l registration number of offending vehicle

l date and day of week

l time of day

l location

l frame counter

l camera identification

All camera system clocks will be synchronised with thenational time-signal transmitted from Rugby.

The steering group controlling the project is attended byrepresentatives of the Government Office for London;Department of Transport (now DETR), including theirPolice Liaison Officer; Home Office, including the PoliceScientific Development Branch (PSDB); MetropolitanPolice; London Transport Buses; and more recently, theAssociation of London Government. The MetropolitanPolice representative also acts as a liaison with theAssociation of Chief Police Officers (ACPO) TrafficEnforcement Technology Sub-committee.

4 Automatic Numberplate Recognition(ANPR) systems

4.1 Introduction

Camera-based traffic enforcement systems have been inuse for 30 years. Whilst they can provide wider coveragethan the equivalent value of resources dedicated to manual

detection, the human effort does not end with theinstallation and maintenance of the equipment. Thenumberplates of the vehicles captured in the photographsstill need to be read manually before a penalty notice canbe issued. With a large number of violators such a processbecomes laborious and in recent years attention has beenfocused on producing an electronic system that canreliably read the numberplate of a moving vehicle.

Automatic number-plate recognition systems were firstdeveloped about 15 years ago. The number of companiesinvolved in the field has increased in the last few years,largely because of the interest in automatic vehiclesurveillance operations and speed violation detection anddeterrence. ANPR systems have also been used to monitortraffic patterns in the UK and the USA.

ANPR systems identify the number-plate within a videoimage of the front of the vehicle by searching for areas with ahigh contrast ratio. The number-plate image is then segmentedinto individual characters. Methods vary for reading thecharacters. Some use neural network principles, which involvetraining the system by example on a large number of repetitionsof a character set. Other systems use template matching, inwhich the characters are compared with internally heldcharacter shapes, or a rule-based approach, which involvescomparing the distinctive characteristics of individualcharacters. Most systems use post-processing to check whetherthe number identified is a valid sequence of characters.

Appendix B provides a comprehensive list of theregistration mark syntax systems used in Great Britain,Northern Ireland and the Channel Islands.

In a previous study, TRL evaluated four ANPR systemswhich in this report are labelled, A, B, C and D. Two ofthe systems used neural techniques, one used statisticalanalysis with fast fourier transforms, the other usednormalised non-linear cross correlation.

4.2 Analysis of Automatic Numberplate Recognition(ANPR) system errors

Analysis of the data-sets and video-tapes was undertakento address the following questions:

l What factors cause the ANPR systems to mis-readnumber-plates?

l Which characters are most often mistaken for each other?

Data sets from systems A, B and C were analysed alongwith data from system C1, a variation of system C but with areduced specification using three, rather than five digitalsignal processing units per camera input. This system wasequipped with infra-red illuminators for night-time use.Analysis of the output from this system is split according tothe lighting conditions. The results from system D were ofinsufficient quality to carry forward to the further analysis.

Sample sizes varied across the data sets that wereanalysed. System B is unable to process video input andwas therefore evaluated in-situ against video footage froma separate TRL video camera. This generated the smallestsample of only 1395 numberplates. System C tested in theinitial trial was shown a relatively large sample of 3030numberplates. Collectively the systems were shown a totalof 9567 numberplates.

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4.2.1 MethodologyThe numberplates as read by the ANPR systems weresequentially matched against those read manually from thevideo-tapes. There were two stages to the matchingprocess. In the first stage, a computer algorithm matchedthe numberplates that had been correctly read by theANPR systems with the corresponding numberplates asread by the human observer, inserting blank spaces into thedata files as necessary. In the second stage the mis-readplates were manually matched with their correspondingplates. The result was two synchronised columns of data,one containing the numberplate of each vehicle on thevideo-tape, the adjacent column containing thenumberplate as/if read by the ANPR system. It was thenpossible to determine whether the ANPR system:

l read the numberplate correctly

l read the numberplate incorrectly

l did not report an attempt at reading the numberplate

A human observer scanned through the video-tapes andfor each numberplate that was read incorrectly, classifiedthe cause of the mis-read into one of five categories andthen noted which single characters had been mistaken foreach other by the ANPR system.

4.2.2 ResultsTable 1 presents the results from the analysis of the causesof mis-reads. The results for systems A and C should beinterpreted as an indication of the systems’ abilities to readnumberplates from a video-tape; it is expected that therecognition rate for live images from the suppliers’cameras would be higher.

In each sample there were a number of instances wherethe systems did not report an attempt at reading a plate.This aspect of the systems’ performance can be explainedby the following three factors.

1 The systems did not have an external triggering system toregister the presence of a vehicle in the field of view of thecamera and relied instead on their ability to detect high-contrast areas in the video images. As a result some vehicleswith very dirty numberplates may have escaped detection.

2 The digital signal processing units may have been busyprocessing the previous numberplate when the vehiclepassed through the field of view of the camera i.e. thesystem lacked sufficient processing power. Increasingthe number of digital signal processing units dedicatedto each camera input would reduce the frequency of thistype of failure.

3 The system might not have reported its attempts atreading the numberplate because its confidence in theattempts did not meet the required threshold. Aconfidence value for each attempt is calculated from acombination of the outputs from the character recognitionand registration mark syntax checking processes.

A breakdown of the causes of the systems’ mis-reads isgiven in the bottom section of Table 1. Owing to the lowresolution of video images in some cases it was difficult todetermine the exact nature of the cause of the mis-read. Inparticular it proved difficult to distinguish between dirt andthe fixings used to secure the numberplate to the vehicle.In such cases, judgement had to be employed on the part ofthe human observer, a fact which is reflected in the results.

In the majority of cases there was no apparent fault withthe plate that was mis-read i.e. when the plate wasexamined on video it was clean and the registration markwas easily distinguishable by the human observer.

Across the samples between 10% and 24% of mis-readswere attributed to a general build up of dirt on the plateand between 6% and 21% of mis-reads were attributed tothe use of fixings.

Other mis-reads were categorised as being caused by theplate being obscured by part of the vehicle, the plate beingbroken, or the use of an unusual style of lettering or badcharacter spacing. In all of the samples these categoriesaccounted for fewer mis-reads than dirt or the use of fixings.

An analysis of the 1344 numberplates which werecommon to the samples shown to the three systems in theinital trials revealed that 7% of the numberplates were notread correctly by any of the systems.

Character read accuracy statistics were calculated foreach system by dividing the number of times eachcharacter had been mis-read by the number of occurrences

Table 1 Analysis of the causes of ANPR system mis-reads

System

C1 C1A B C (Daylight) (Infra-red)

Total sample size (numberplates) 2323 1395 3030 2331 488

Numberplate read correctly 1524 (65.6%) 942 (67.5%) 2291 (75.6%) 1569 (67.3%) 313 (64.1%)No answer reported 319 (13.7%) 178 (12.8%) 487 (16.1%) 527 (22.6%) 103 (21.1%)Numberplate read incorrectly 480(20.7%) 275 (19.7%) 252 (8.3%) 235 (10.1%) 72 (14.8%)

Cause of numberplate mis-read:No apparent fault with numberplate 64% 56% 61% 67% 60%Numberplate was dirty 20% 24% 10% 15% 18%Numberplate fixings 6% 8% 21% 9% 17%Numberplate obscured by part of vehicle 4% 7% 1% 5% 0%Plate was broken or cracked 4% 3% 8% 3% 3%Unusual style of lettering / character spacing 1% 3% 0% 1% 1%

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of the character in the sample. Table 2 shows the fifteencharacters with the lowest average read accuracy.

Appendix C contains tables giving the character readaccuracies for each system with the characters that eachwas mistaken for.

vehicle are less likely to cause a human observer to mis-read anumberplate than a computer-based recognition system;humans can easily distinguish between the fixings andcharacters on a numberplate. Altering the regulations andcriteria to specify fixings that match the colour of the part ofthe plate that they pass through might reduce the number ofANPR mis-reads caused by the fixings.

A high number of mis-reads occured even though therewas no apparent fault with the numberplate. At presentthere is no standard character font for displaying vehicleregistration marks in the United Kingdom. Consequentlyneural network and template matching ANPR systemshave to be trained to read a number of fonts, reducing theirability to distinguish between similar characters. TheLicensing and Roadworthiness Policy Division of theDepartment of Transport are planning new regulations fornumberplates with the main aim of introducing a single,mandatory character font. Introduction of a single fontshould increase the accuracy of ANPR systems.

The choice of font could prove to be crucial to thesuccess of an enforcement system based on ANPRtechnology. Figure 1 illustrates two fonts developed foruse with optical character recognition systems.

The adoption of such a font for numberplates couldsignificantly reduce the error rates of ANPR systemsbecause the characters bear less resemblance to each otherand therefore the systems would be less susceptible toconfusion from noise, e.g. dirt on the numberplate, adverseweather conditions.

The results detailed above are based on ANPR systemswhich although not optimised for enforcement, illustratesome of the problems likely to be encountered in practicewhen using video based systems for enforcement.

In the short to medium term, the only practical methodof violator identification will involve video images, so it isimportant to understand the characteristics and limitationsof video systems.

ANPR systems cannot guarantee to read allnumberplates but, as processing power and algorithmsimprove, they can be expected to approach the readingaccuracy of a human observer and thus can be expected tohave a role in the overall enforcement process.

Table 2 Mis-read characters sorted by read accuracy

Character Read accuracy

Q 50.0%Z 60.0%O 84.8%C 93.6%D 94.9%6 95.3%5 95.9%8 96.0%I 96.4%9 96.4%B 96.7%S 96.7%W 96.8%0 (zero) 96.9%7 96.9%

4.2.3 Discussion of resultsThe relatively low number of mis-reads that were judgedto have been caused by broken plates, the plate beingobscured by part of the vehicle and the use of unusuallettering and character spacing is indicative of theeffectiveness of the M.O.T. Test. The M.O.T. TestInspection Manual (Vehicle Inspectorate, 1995) specifiesthese factors as criteria for failing a vehicle on display ofits vehicle registration mark. Although the manual alsospecifies dirty numberplates as a reason for rejection of avehicle it is perhaps unreasonable to expect a numberplateto remain as clean as it was on the day the vehicle wastested. The build-up of dirt on numberplates is a problemthat is inherent in the use of optical systems to identifyvehicles in an open environment.

Although there are exact regulations for the display ofvehicle registration marks (see Appendix A) these are notexpressed explicitly in the M.O.T. Inspection Manual, and thecriteria for inspecting numberplates are open to interpretation.A vehicle will pass the criteria providing its numberplate(s) isnot ‘likely to be misread or is not easily legible by a personstanding approximately 20 metres to the front/rear of thevehicle’. The fixings used to secure the numberplate to a

OCR - A:

OCR - B:

Figure 1 Examples of fonts that lend themselves to optical character recognition

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5 Electronic licence plate

5.1 Introduction

The results of the statistical study detailed above illustratethe difficulties involved with using video-image processingfor toll enforcement. Electronic licence plates (ELPs) havethe potential to increase the effectiveness of enforcementbecause the rate of successful vehicle identification isconsiderably higher than that of video-image processing.

There have been a number of papers discussingautomatic vehicle identification technology and itspotential applications. The next section is a survey of thepublished literature.

5.2 Electronic licence plates : a literature review

Bergan, Henion, Krukar and Taylor (Bergan et al, 1988) andSommerville (Sommerville, 1991) reviewed the technologiesavailable for automatic vehicle identification and identifiedthree read-only technologies which would be suitable as thebasis of an electronic licence plate system - magnetic induction,radio and microwave transmission and acoustic crystal.

Magnetic induction and radio and microwave transmissionsystems may be classified into three distinct groups accordingto the power source of the vehicle mounted tag. Active tagsystems draw power from the vehicle on which they aremounted. Although they have the advantage of having avirtually unlimited power supply and hence can be detectedover a wider range of lateral positions across the highway, theyhave the disadvantage of being easily disabled by a motoristwho does not wish to be identified. Semi-active tags rely on aninternal battery for power and whilst they are not so susceptibleto tampering, their internal battery ultimately has a limited life-span. Passive tags are energised by an electro-magnetic fieldgenerated either by the inductive loop in the pavement or, in thecase of radio frequency systems, by a separate power loop.

Magnetic induction systems rely on inductive couplingto transfer the data from tag to roadside interrogator viaground loops. The ground loops used are the same as thoseused for traffic signal triggering and vehicle counting andthe technology has the advantage of being relativelymature and inexpensive.

Acoustic crystal (sometimes referred to as surface acousticwave) tags contain a small lithium crystal which can beembedded in the windscreen of the vehicle. The crystal isexcited by either a high-frequency sound wave or a lowpower microwave. The wave is absorbed by the crystal whereit is modified with the vehicle’s identification code and re-transmitted. The main drawback of acoustic wave systems isthat the tag has to be in the line of sight of the interrogator.

Sterzer (Sterzer, 1974) proposed an electronic licence platewhich had three functions - electronic identification of thevehicle, transmission of messages to and from the vehicle andas a transponder for use with co-operative collision avoidanceradar systems. The proposed system was based on second-harmonic reflectors. The plate consisted of a printed-circuitantenna and simple electronics covered by a visual display ofthe licence number of the vehicle. Electronic communicationbetween the vehicle and its surroundings took place at twoharmonically related microwave frequencies.

Communication from the vehicle and its surroundingstaking place at twice the frequency of communicationsfrom the surroundings to the vehicle. From considerationsbased on antenna size, beam width, rf spectrum allocationand rf absorption in air, a base frequency of 10 GHz wasproposed. Sterzer argued that the economic viability of theproposed electronic licence plate system could bedemonstrated by examining its effects on highway safety.

Daniel Avivi, Chief Scientist to the Israeli Ministry ofPolice, proposed a nation-wide electronic licence platesystem for Israel at the 1991 IEEE Carnahan Conferenceon Security Technology (Avivi, 1991). He envisaged thatsuch a system would have a number of applications andwould not just be of interest to the Ministry of Police butto other public and commercial organisations as well. Hesuggested that electronic licence plates could be used for:

l tracking of stolen vehicles

l toll collection

l entrance to restricted areas

l traffic control - priority measures for buses andemergency vehicles

l traffic statistics

l licensing

l weigh-in-motion systems

l fleet control

Avivi argued that privacy would not be lost as a result ofdata collection, but rather in the use to which it is put, andto whom the data is made available. An interministerialsteering committee was established to promote the project.

The Comité Européen de Normalisation TC278 Task Forceon ‘After Theft Systems For Vehicle Recovery’ is examining anumber of technologies to aid the recovery of stolen vehicles.The Sussex Police Force has contributed a survey of therequirements and experience of European law enforcementagencies (Childs and McInnes, 1996). In the report they drewtogether a list of ‘Composite Police Requirements’ including:

2.4. ATSVR [After Theft Systems For VehicleRecovery] systems must conform to Data Protectionrequirements and not infringe personal liberty orprivacy except when the vehicle is stolen or if the lifeof an occupant is threatened.

2.6. The system shall locate the vehicle in ‘realtime’ with a maximum error of 100 metres.

Of passive electronic tags they wrote:

These provide accurate identification, are cheap,easy to install and do not require a power supply.

Against this there are several types of electronic tagavailable and no common scanning device or technicalstandards. Except when the vehicle is stationary at acheck-point or port these tags do not give a real timelocation. In some cases the information on the tag hasto be checked against a private database to obtain allthe information about the owner.

10

The requirements phase of the work has been completedand work is in progress on preparing a European standard.

The final report also contains a survey of requirementsfrom the automobile manufacturer Renault (Jaquet, 1996).Jacquet compared four after-theft system concepts -localization/tracking, remote immobilization, short-rangeidentification with theft sensor and short-rangeidenfication without theft sensor.

In the ‘short-range’ identification approach, the on-board unit is generally very simple and thus low cost.

Identification systems are very strong where costsand independence from the vehicle are concerned.When considering the reaction time and probabilityof detection, however, the identification systemsperform relatively poorly. This could be improved byutilizing a built-in theft detector and by increasingthe number of fixed and portable readers.

The issue of resistance to sabotage is more or lessdisappointingly addressed by all approaches. Ifidentification systems offer good performances whenmade mandatory by law, the situation is just as bad aswith other approaches when this condition is nolonger valid.

It clearly appears that none of the existingapproaches performs well in all criteria. Underthese circumstances, Renault’s point of view is tofavour simplicity and costs of on-board units.

There have been two large scale implementations ofelectronic licence plate systems - the HELP program in theUnited States and the Electronic Road Pricing pilot studyin Hong Kong.

5.2.1 HELP program, CRESCENT demonstration projectand PrePass

The HELP (Heavy-Vehicle Electronic License Plate)Program originated out of a concept study undertaken toexamine ways of increasing the efficiency of freightmovements through Arizona’s ports of entry. A system wasproposed which utilised automatic vehicle identificationtechnology along with weigh-in-motion sensors and pre-certification. It quickly became apparent that there waswidespread support for the concept and the HELP programwas formed by a consortium of 14 state government agenciesand the Port Authority of New York and New Jersey withsupport from the Federal Highways Administration (FHWA).Automatic vehicle identification technology was assessedwith a five stage test program between 1985 and 1989.

Eight AVI equipment manufacturers submitted systemsfor testing in the first phase of the program. This stageconsisted of test-track trials at the Ford Proving Ground atYucca, Arizona by the Arizona Department ofTransportation. The test-track trials concentrated onassessing the effects of tag positioning, speed of vehicleand operating the system on a multi-lane highway or withmore than one transponder fitted to a vehicle. Data fromthe first phase of testing was analysed and conclusionswere reached about which systems had the highest

probability of satisfying the requirements of the HELPprogram. Four systems were selected for more extensivetesting in stages two and three.

The second stage of testing, conducted at theTransportation Laboratory of the California Department ofTransportation, consisted of laboratory condition testsexamining the effects of electrical interference and noise(using a signal generator), attenuation, harsh environmentalconditions, speed and position of transponder. This stage alsoincluded extended accuracy tests designed to assess the abilityof the systems to produce consistently accurate transponderreadings over a relatively high number of passes.

The third stage, conducted by Oregon State Universityand the Oregon Department of Transportation, addressed theperformance of the systems in a ‘real-world’ situation. Thesystems were installed at open-highway sites in Oregon. Thefield testing was divided into two distinct elements. The firstwas designed to test particular aspects of the systems’operation including transponder placement, speed ofvehicle, multi-lane highway conditions, multi-transponder,power failure and external interference e.g. Citizens’ Bandradio, cellular telephones, portable generators. The secondelement was a ‘routine data collection program’ in whichvolunteer companies fitted transponders to their vehicleswhich regularly passed the field testing sites.

Data from the three phases were gathered and analysedand a generic equipment specification was drafted for thefinal phase of testing. Semi-active transponders werespecified because it was believed that reader power outputlevels for a passive system would approach or exceedregulatory or advisory health and safety limits in manycountries. Vendors who wished to submit a passive systemfor testing would have to demonstrate that radiated powerlevels were no higher than those specified for inductionand microwave triggered semi-active transponder systems.

In the fifth and final phase of testing, prototypeequipment manufactured in accordance with the draftspecification was tested in field trials (similar to phasethree) to verify the performance of a system built to thedraft specification against the performance criteria set inthe draft specification. It was found that systems based onradio frequency technology performed better thaninductive systems. Radio frequency based system readfailures were observed in tests involving multipletransponders, multiple vehicles, in-vehicle cellulartelephones and road-side electrical generators. The HELPprogram chose to exclude inductive systems from the finalspecification, opting to specify a semi-active 915 MHzradio frequency system.

After a successful demonstration phase the HELPprogram moved into the private sector as Heavy VehicleLicense Plate Inc. who now offer the pre-clearance serviceunder the trade-name PrePass. HELP Inc. sites are nowoperational in 11 states across the U.S.

5.2.2 Electronic Road Pricing (ERP) project, Hong KongThe Electronic Road Pricing (ERP) pilot project (Catling,1995) was carried out in Hong Kong between 1983 and1985 by Transpotech (a government owned companyestablished to disseminate the skills and resources of the

11

Department of Transport and the then Transport and RoadResearch Laboratory). The primary objective of the projectwas to demonstrate the technical viability of an AVI basedroad-pricing system given the rigorous requirements forreliable and secure handling of toll transactions. The AVItechnology which had been researched at the TRRL in the1970s had been further developed by Plessey Controls Ltdfor use on the Glasgow Underground, and with theadvances in microelectronics in the early 1980s it hadbecome clear that it might have been possible toimplement an affordable system which could operate in theharsher environment that road-traffic presents.

The electronic numberplates used for the pilot studycomprised a robust, passive electronic transponder whichcould be fitted to the underside of a vehicle inapproximately five minutes. The ENP was approximatelythe size of a video-cassette and weighed 1200 grammes.Being a passive device, it required no power supply,drawing power from an electro-magnetic field generated bythe reader sites. Each ENP was coded with a uniqueidentification code, independent of any vehicle registrationnumber. The ENP consisted of two custom-designedintegrated circuits, two standard integrated circuits, a smallnumber of discrete components and three ferrite aerials forthe reception and transmission of the signals. The ENPswere interrogated by aerials laid within the road-surface. Asingle power loop stretched across the full-width of thecarriageway energised the ENPs. An array of dual-purposereceiver/detector loops was positioned on the downstreamside of the power loop to (a) detect the presence of a vehicle(b) receive data transmitted from vehicles fitted with ENPs.An enforcement system correlated data from the detectionand receiver loops and alerted the enforcement system to thepresence of any vehicle which was not fitted with an ENP.Closed-circuit television technology (supplied by GECAvionics) was used to capture images of violating vehicles.A total of 2,600 vehicles were equipped with the electronictags for the pilot study. 1,300 of these were government-owned vehicles, approximately 700 were buses and the restof the sample comprised of volunteers who regularly usedthe trial area.

The ENPs used for the pilot study proved to be reliable.At the start of the project it was expected that there wouldbe less than 1000 ENP failures per year, plus a smallnumber of failures caused by physical damage, vehicleaccidents etc. With a sample of 2600 vehicles, less thanone failure every two months was expected. During thesix-month ENP evaluation stage only three faulty ENPswere identified.

The results obtained from the pilot-stage of the projectwere used to define a performance specification which wasconsidered more than adequate for a full system, whilstremaining economically achievable with the then currenttechnology. The performance specification of the systemrequired that the chances of the wrong vehicle owner beingcharged for a toll crossing was 1 in 10 million.

Although the system was believed to be technicallyfeasible and the results of the experiment were positive,owing to the political climate in Hong Kong at the time afull-scale system was never implemented.

6 Summary and conclusions

The use of photographic and video images for enforcementof traffic related violations has been increasing rapidlysince the technology is becoming more cost-effective andthe legal and institutional issues are being resolved. HomeOffice approval of video based systems and the evidentialrequirements have been developed from those in place for‘wet film’ systems, although newer systems have yet to befully tested in court.

In the short to medium term, the only practical methodfor identification of tolling offenders will involve videoimages, so much can be learnt from recent police andHome Office experience. However, if, as seems likely, atolling violation is a civil rather than criminal act, then theDepartment of Transport, rather than the Home Officewould be responsible for equipment type-approval and theenforcement process.

The findings detailed in this report illustrate some of theproblems likely to be encountered in practice when usingvideo based systems for enforcement. Understanding thelimitations of the technology is therefore important.

One technique, closely linked with video imaging in thiscontext is automatic numberplate reading. ANPR systemscannot guarantee to read all numberplates but, asprocessing power and algorithms improve, they can beexpected to approach the reading accuracy of a humanobserver and thus can be expected to have a role in theoverall enforcement process.

Since identification of numberplates cannot beguaranteed by visual means, an ‘electronic licence plate’offers an alternative, complimentary means of vehicleidentification which could be attractive. Studies to datehave identified some potential advantages and technologyoptions. Trials have been limited to specific applicationsand no recent UK work has been identified. There are,however, signs of increasing interest in ELPs for vehiclesecurity, which may provide a compelling customer drivenreason for their introduction.

Electronic licence plates have the potential to assist intolling enforcement (and in a number of other security andenforcement applications). Clearly their introduction intothe UK would require considerable and wide rangingstudies. Within the tolling enforcement context, it isproposed that a number of technology trials be undertakento understand more fully the potential and limitations ofsuch devices for the UK.

Numberplates, scanned either visibly or electronically,remain the only practical means of identifying motorwaytoll violators. This report has summarised the ‘state-of-the-art’ and demonstrated that 100% enforcement is notcurrently achievable for a range of technical reasons (aswell as legal, institutional and commercial ones). It istherefore proposed that technical investigations andevaluations are undertaken on both video-based systemsand electronic licence plates to better understand their rolein enforcement.

12

7 References

Avivi D (1991). Automatic vehicle identification - AVI -electronic license plates: The public safety perspective.1991 IEEE Carnahan Conference On Security Technology

Bergan A T, Henion L, Krukar M and Taylor B (1988).Electronic license plate technology: automatic vehiclelocation and identification. Canadian Journal Of CivilEngineering 1988

Blythe P T and Burden M J J (1996). The technical andinstitutional issues associated with the enforcement of a multi-lane debiting system. (University of Newcastle upon Tyne).

Castle Rock Consultants (1990). Heavy vehicleelectronic license plate (HELP) Program, Final Report.

Catling I and Harbord B (1995). Electronic road pricingin Hong Kong. Traffic Engineering & Control (December1995)

Childs R and McInnes A (1996). Law enforcementagencies requirements and experience. (Report preparedfor TC278 Task Force on ‘After Theft Systems ForVehicle Recovery’).

Harbord B and Jones J (1996). Variable speed limitenforcement - the M25 controlled motorway pilot scheme.Camera Enforcement of Traffic Regulations, Colloquiumorganised by Professional Group C12 (Transportelectronics and control) Monday 18 November 1996.Digest No 96/252.

Jaquet I (1996). Survey of requirements from AutomobileRenault. (Report prepared for TC278 Task Force on ‘AfterTheft Systems For Vehicle Recovery’).

Lewis S R (1996a). Future system specifications for trafficenforcement equipment. Camera Enforcement of TrafficRegulations, Colloquium organised by Professional GroupC12 (Transport electronics and control) Monday 18November 1996. Digest No 96/252.

Lewis S R (1996b). Home Office and ACPO TrafficOutline requirements and specifications for automatictraffic enforcement systems. PSDB Publication No 3/96.

Lewis S R (1996c). The bus lane enforcement camerahandbook provisional. PSDB Publication No 17/96.

Robertson D and Kadir O (1996). The road to HomeOffice type approval. Camera Enforcement of TrafficRegulations, Colloquium organised by Professional GroupC12 (Transport electronics and control) Monday 18November 1996. Digest No 96/252.

Sommerville F (1991). Applications of automatic vehicleidentification technology. Transport Reviews 1991

Sterzer F (1974). An electronic licence plate for motorvehicles. RCA Review. vol.35 June 1974.

Turner D and Monger P (1996). The bus laneenforcement cameras project. Camera Enforcement ofTraffic Regulations, Colloquium organised by ProfessionalGroup C12 (Transport electronics and control) Monday 18November 1996. Digest No 96/252.

Vehicle Inspectorate (1995). The M.O.T. InspectionManual.

13

Appendix A: Standards for the display of vehicle registration marks

14

15

Great Britain

Great British vehicle registration marks conform to the following syntaxes:

A 1 111 A AAA 1 Y111 AA AAA 11 Y

AA 1 111 AAA AAA 111 YAA 11AA 111 1111 A Y 1 AAAAA 1111 1111 AA Y 11 AAA

1111 AAA Y 111 AAAAAA 1AAA 11AAA 111

where: 1 represents any numeric characterA represents any letter excluding the letters I, Q and ZY represents any letter excluding the letters I, O, U and Z

Diplomatic registration marks conform to the syntax:

111D111 i.e. the letter ‘D’ with sets of three numbers either side

Consulate registration marks conform to the syntax:

111X111 i.e. the letter ‘X’ with sets of three numbers either side

Northern Ireland

The Driver and Vehicle Licensing Authority in Northern Ireland has issued registration marks with the following syntaxes :

IA 1 AZ 1 AIA 1 AAZ 1IA 11 AZ 11 AIA 11 AAZ 11IA 111 AZ 111 AIA 111 AAZ 111IA 1111 AZ 1111 AIA 1111 AAZ 1111

1 IA 1 AZ AAI 111 IA 11 AZ AAI 11111 IA 111 AZ AAI 1111111 IA 1111 AZ AAI 1111

where: A represents any letter1 represents any digit

Jersey

The Jersey vehicle licencing authority issues registration marks which conform to the following syntaxes:

J 1J 11J 111J 1111J 11111

i.e. the letter J followed by up to 5 digits

Guernsey

The Guernsey vehicle licencing authority issues registration marks which simply consist of up to 5 digits.

Alderney

Vehicle registration marks issued on the island of Alderney conform to the following syntaxes:

AY 1AY 11AY 111AY 1111

i.e. the letters AY followed by up to 4 digits

Appendix B: Vehicle registration mark formats in use in the United Kingdom

16

17

Tab

le C

1 C

hara

cter

rec

ogni

tion

erro

rs —

Sys

tem

AAppendix C: Tabulated results from the analysis of automatic numberplate

recognition system errors

18 Table C2 Character recognition errors — System B

19

TableC3 Character recognition errors — System C

20 Table C4 Character recognition errors — System C1–Daylight

21

Table C5 Character recognition errors — System C1–infra-red

22

Appendix D Processing paths for parking tickets and fixed penalty notices

PCN ISSUEDBY P.A.

BOROUGH PARKINGADMINISTRATION

BOROUGH PARKINGMANAGEMENT

TICKETPROCESSING UNIT

PAYMENTNOT RECEIVED

DVLAENQUIRY

PCNCLEARED

HONESTYPAYMENT

BOROUGH PARKINGADMINISTRATION

PCNCLEARED

NOT REGISTEREDINCORRECT VRM

PAYMENTRECEIVED

NOTICETO OWNER NFA

BOROUGH PARKINGMANAGEMENT

PAYMENTNOT RECEIVED

REPRESENTATION NEW OWNERSUPPLIED

NEW OWNER NOT SUPPLIED

ANY OTHERGROUNDS

STATUTORY

NONSTATUTORY

PCNCLEARED

ACCEPTEDLETTER SENT

ACCEPTEDLETTER SENT

REJECTEDLETTER SENT

PAYMENTRECEIVED

PAYMENTNOT RECEIVED

BOROUGH PARKINGADMINISTRATION

REJECTED LETTER SENTINC. APPEAL EXPLAINED

DENIAL OFOWNERSHIP

APPEALRECEIVED

PAPERS TO PARKINGADJUDICATOR ADMIN.

ADJUDICATORDECIDES

REJECTEDLETTER SENT

COUNTYCOURT

INSTRUCTBAILIFFS

TICKET PROCESSING PATH

23

OFFENCE REPORTED

NOTIFICATIONRECEIVED IN CTOAND INPUT TO TTS

DVLA ENQUIRY

DVLA RESPONSE

NIP/963PRODUCED AND

SENT OUT

NOMINATION

CORRESPONDENCE ADDRESSEE GIVENx DAYS TO RESPOND

NFA

NO OWNER/KEEPER DETAILS

ENQUIRIES

DENIAL OFOWNERSHIP ETC.

NFA

ADMISSION

COFP PRODUCEDAND SENT OUT

NO RESPONSE

REMINDERLETTER SENT

ENQUIRIES

PROCESSFOR FAILURETO DISCLOSE NOT PAID

WITHIN SEP

ADDRESSEE GIVENx DAYS TO RESPOND

CORRESPONDENCE

PAY

NFA

R/D CHEQUENOTIFICATION

CONFIRMEDPAYMENT

REVERTED TOPROCESS

PROCESSING PATHConditional offers of fixed penalty

24

Abstract

A key issue for the successful operation of a UK motorway tolling system is the enforcement of payment. The firststage of this enforcement process requires identification of violators. At present, it is anticipated that this will beundertaken by visible identification of violator vehicles and the tracing of the person responsible through the vehicleregistration mark. This report surveys vehicle registration marks and summarises some of the legal issuessurrounding the capture and transmission of video images for enforcement purposes. The performance of a numberof commercially available automatic numberplate reading systems is then examined and their role in theenforcement process discussed. An alternative method of numberplate identification based on an ‘ElectronicLicence Plate’ is also discussed.

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For further details of these and all other TRL publications, telephone Publication Sales on 01344 770783 or 770784,or visit TRL on the Internet at http://www.trl.co.uk.