MIDLAND, TEXAS is located in the heart of theoil and gas rich Permian Basin. In 2005 theCity began to experience exponential growthas the national and global demand for energysoared and exploration and productionactivates increased. The population of about100,000 began growing 10% annually. In 2007year over year traffic volume at major arterialsin the City increased by 17% and trafficmanagement became a top priority.The City’s existing traffic management system

installed in the early 1990s was at end-of-life.It had been installed as two separate systems.Major arterials were managed by fixed timeintervals for peak inbound and outbound trafficflows. The downtown system was controlled bya grid and changed traffic signals at fixedintervals set independently for inbound andoutbound traffic, and by time of day.Replacement parts were scarce and operationsand maintenance costs were increasing due tothe need for more manual intervention. Thedecision to assess options and select anadvanced traffic management system (ATMS)was initiated by Gary Saunders who heads theCity Traffic Engineering Department.

Wireless is the solutionSaunders recommended the IP wireless ATMSproposed by Naztec, Inc. The solution used theNaztec model 980 controller and the web-basedATMS Central Software Suite running on a Ciscowireless network. In 2008 the trafficdepartment began working with Naztec andColeman Technologies Inc., a Cisco Goldpartner, to handle the site survey, final designand implementation.The re-vamped city-wide system began

operation at the beginning of March this yearusing 180 Cisco 1524 wireless access points.Licensed frequencies are used to provide thebackhaul for the 200Mbps network and providetwo way communications with the Nazteccontrollers.The system monitors, manages, and notifies

the traffic department about the status of 119networked traffic signals and 70 pedestriancrosswalk flashers. An additional 29 solarpowered flashers will be added when thedepartment identifies the best solution topower both the radios and the flashers. Thesystem backbone runs to a new centralisedTraffic Management Centre (TMC) that wasimplemented as part of the project.Arterial management applications use the IP

network to detect traffic flow and then takerapid pre-emptive action to mitigate

congestion. IP-connected controllers sendimmediate notification of signal malfunctionand enable remote management to resolvesignalling problems, optimise traffic flow bychanging signal offsets and splits, and adjustthe traffic signals for major events affectingtraffic.Secure monitoring and management can be

done via web-enabled devices at the intersec-tions and connected in what is effectively anextended wireless LAN. This permits trafficpolices which can be programmed to respond

to predefined conditions. For example, a vehiclethreshold policy could be set for key intersec-tions. When the count exceeds the thresholdthe system can recalculate signal splits andoffsets and automatically apply them.‘By having the automated system analyze

issues, I estimate that we will be able to reducethe amount of time spent on troubleshootingand problem resolution by at least 30%.‘By reducing manual intervention, we also

reduce fuel costs for the City. Motorists willexperience fewer delays, reducing carbonemissions and enabling drivers to gain betterfuel mileage. Collectively these savingstranslate in to millions of dollars a year’ saysGary Saunders, City of Midland transportationmanager.Mr Saunders estimates the following cost

savings and benefits as a result of the newATMS: 27% reduction in total delays pervehicle, 18% reduction in total stops pervehicle and 10% reduction in fuel consump-tion. This adds up to $1.2m annual savings onfour major arterials alone with averagevehicular volume. Following the first threemonths of operation, actual values appear tobe in line with these estimates.

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Wireless traffic managementnetwork for downtown renewal

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IEB52_p31:IEB 1/5/09 18:26 Page 31This case study was first published in the publication 'industrial ethernet book':http://www.iebmedia.com/index.php?id=6092&parentid=74&themeid=275&hpid=2&showdetail=true&bb=1&appsw=1

IP-video is the futureThe next step will be to add wireless IP videocameras to the system. Five pan, tilt, zoom(PTZ) cameras are being tested to stream livevideo feeds from field locations back to theTMC. This will enable the department tomonitor high accident intersections. Earlyaccident detection enables quick informationtransfer to emergency dispatch and thererouting of traffic on the fly. The departmentestimates that 70 cameras should provide fullcity-wide coverage for transportation-relatedservices.Other departmental needs for cameras are

being identified. The police department needsto monitor security in public spaces and coulduse the video to integrate into applicationssuch as license plate recognition. Addition ofsensor based technology and analytics couldalert cameras to hazardous material spills orfires and direct cameras in the impactedvicinity to provide visual support for responseand remediation efforts.‘Based on my past experience with wireless

systems, I didn’t realise how fast informationcould really be transmitted. I assumed that thestreaming video would hesitate, but in fact wecan watch traffic as clearly as watching a DVD.‘It is an amazing thing when you invest in

the right technology and you can actually seethe limitless possibilities unfold in front ofyou’ said Eric Johnson, assistant transporta-tion manager, City of Midland

Strategic positioningThe decision has broad implications for thefuture of mobile applications for the City. The$1.9m investment will cover the network costfor the ATMS, but it also provides the wirelessnetwork as a platform for a growing array ofemerging technologies that will benefit theentire city. Downtown revitalisation is seen asa key economic development initiative for theCity and the installed network technology mayhave a role to play. As a result of the decisionmade by traffic engineering, the downtown areanow has 95% wireless coverage at no additionalcost. Free 802.11 WiFi access could be extendedto outdoor spaces to increase the attraction ofthe downtown area as a destination.The value proposition for the City is clear.

Either pay for separate departmental networksor invest in a single, scalable, converged IPnetwork. With the proliferation of mobiledevices, the need for a secure, centrallymanaged, multiservice network is rapidlybecoming a critical success factor. The Midlandmodel offers a great example of a City thatunderstands the strategic value of the IPnetwork as a platform. Barbara Walker

www.cisco.com

Barbara Walker is territory account manager,North Texas Public Sector, Cisco Systems

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Fast wireless roamingassists railway control

EVERYTHING WORKS WELL as long as the trainis standing still… The IEEE802.11b/g wirelessLAN could provide a money-sensible method ofexchanging data bursts with moving objects suchas surface and underground railways – exceptthat conventionally, it takes some three to fiveseconds to establish a network connection.Network infrastructure company Moxa has

done some original development work on thesoftware mechanics of key exchange in itsaccess points, the results of which promise tobring a more cellular style of roaming towireless LAN access points. By re-organisingthe way that the security tokens are exchangedbetween a client and successive access pointsbelonging to the same network, the handovertime between access points can be as little as100ms – provided that both the APs and theclient incorporate Moxa’s software tweak. Evenwhere the link involves another company’s APand a TurboRoaming client – which is what thecompany calls its technology – the acquisitiontime can be reduced to around 500ms, it claims.Of course this is not, and was never intended

to be a technical development which coulddisplace other cellular technologies: the 100meffective range for 802.11a/b/g for client-access point linkage still applies. However, itdoes permit a moving client to be part of aconventional network if only in brief bursts.Translated into a railway application with a

string of suitably equipped APs set out alongthe platform, high speed duplex data exchangecan take place between the train and thetrackside at speeds up to 100km/hour.

In practiceCommunication Based Train Control (CBTC) is aan automated railway signalling system beingdeployed in modern metro systems around theworld. It is designed to provide immediatestatus updates and control aspects of a railwaysystem. Due to the mobile nature of the appli-cation, CBTC uses WLAN as its basis. Trains canupdate their status immediately to the controlcentre via WLAN and also receive commandsfrom the control centre.The application requirements include wireless

communication capability at speeds up to100km/hr, short system recovery time forseamless wireless connectivity, STP/RSTPprotocol to resume communication when awired or wireless link fails and EN50155compliance for electronic equipment used onthe rolling stock.

Solution descriptionThe CBTC system should include access points(AP) placed about 200 metres apart from eachother along the track. For network redundancy,two access points should be placed in the sameplace and all APs are connected to the controlcentre via fibre cables. Each train also containstwo APs onboard: one at the head and theother at the tail end.To ensure proper communication, the APs

need to work properly up to at least 80 to100km/hour. The roaming switch time mustalso be less than 500ms for this kind of appli-cation while the total delay from the train tothe control centre must also be under twoseconds. Vibration protection is also important.In metro systems, the EN50155 certificationfor railways may serve as a reference for thiskind of application.

The technology for clientroaming across a WLAN is gettingbetter. The handover time from APto AP can be as short as 100msunder optimal conditions

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