Road User Effects

The World Bank

Rodrigo Archondo-CallaoETWTR

Representative Vehicles• Motorcycle• Small Car• Medium Car• Large Car• Light Delivery Vehicle• Light Goods Vehicle• Four Wheel Drive• Light Truck• Medium Truck• Heavy Truck• Articulated Truck• Mini-bus• Light Bus• Medium Bus• Heavy Bus• Coach

• Bicycles• Rickshaw• Animal Cart• Pedestrian

MotorizedTraffic

Non-Motorized Traffic

Road User Costs Models• Fuel• Lubricant oil• Tire wear• Crew time• Maintenance labor• Maintenance parts• Depreciation• Interest• Overheads

• Passenger time• Cargo holding time

Vehicle Operating Costs

Time Costs

Accidents Costs

Vehicle Speed and Physical Quantities

Road Roughness and Terrain and Vehicle Characteristics

Vehicle Speed

Physical Quantities Unit Costs

Road User Costs

Terrain Characteristics: Rise Plus Fall and Horizontal Curvature

Vertical Profile

Horizontal Profile

Rise Plus Fall = (R1+R2+R3+F1+F2) / Length(meters/km)

Horizontal Curvature = (C1+C2+C3+C4) / Length(degrees/km)

Physical Quantities

Component Quantities per Vehicle-km

Fuel litersLubricant oil litersTire wear # of equivalent new tiresCrew time hoursPassenger time hoursCargo holding time hoursMaintenance labor hoursMaintenance parts % of new vehicle priceDepreciation % of new vehicle priceInterest % of new vehicle price

Free-Flow Speeds Model

• VDRIVEu and VDRIVEd = uphill and downhill velocities limited by gradient and used driving power

• VBRAKEu and VBRAKEd = uphill and downhill velocities limited by gradient and used braking power

• VCURVE = velocity limited by curvature• VROUGH = velocity limited by roughness• VDESIR = desired velocity under ideal

conditions

Free speeds are calculated using a mechanistic/behavioral model and are a minimum of the following constraining velocities.

Free-flow Speed and Gradient

0

50

100

150

200

250

300

-10 -8 -6 -4 -2 0 2 4 6 8 10

Gradient (%)

Spe

ed (

km/h

r)

Roughness = 3 IRI m/kmCurvature = 25 degrees/km

VCURVE

VROUGH

VDESIR

VDRIVE

VBRAKE

Speed

VDRIVE

Drive Force

Grade Resistance

Rolling Resistance

Air Resistance

- Driving power- Operating weight- Gradient- Density of air- Aerodynamic drag coef.- Projected frontal area- Tire type- Number of wheels

- Roughness- Texture depth- % time driven on snowcovered roads- % time driven on watercovered roads

VROUGH

VROUGH is calculated as a function of roughness.

VROUGH = ARVMAX/(a0 * RI)

RI = Roughness

ARVMAX = Maximum average rectified velocity

a0 = Regression coefficient

VDESIRVDESIR is calculated as a function of road width, roadsidefriction, non-motorized traffic friction, posted speed limit, and speed enforcement factor.

VDESIR = min (VDESIR0, PLIMIT*ENFAC)

PLIMIT = Posted speed limitENFAC = Speed enforcement factorVDESIR0 = Desired speed in the absence of posted speedlimit

VDESIR0 = VDES * XFRI * XNMT * VDESMUL

XFRI, XNMT = Roadside and NMT factorsVDESMUL = Multiplication factorVDES = Base desired speed

Traffic Flow Periods

To take into account different levels of traffic congestion at different hours of the day, and on different days of the week and year, HDM-4 considers the number of hours of the year (traffic flow period) for which different hourly flows are applicable.

PeakNext to Peak

Flow Periods

Medium flowNext to LowOvernight

Flow

Number of Hours in the Year

Passenger Car Space Equivalent (PCSE)

To model the effects of traffic congestion, the mixed traffic flow is converted into equivalent standard vehicles. The conversion is based on the concept of ‘passenger car space equivalent’ (PCSE), which accounts only for the relative space taken up by the vehicle, and reflects that HDM-4 takes into account explicitly the speed differences of the various vehicles in the traffic stream.

Motorcycle 0.50 Medium Truck 1.40Small Car 1.00 Heavy Truck 1.60Medium Car 1.00 Articulated Truck 1.80Large Car 1.00 Mini-bus 1.20Light Delivery Vehicle 1.00 Light Bus 1.40Light Goods Vehicle 1.00 Medium Bus 1.50Four Wheel Vehicle 1.00 Heavy Bus 1.60Light Truck 1.30 Coach 1.70

Speed Flow Model

To consider reduction in speeds due to congestion, the “three-zone” model is adopted.

Speed (km/hr)

S1

S2

S3

Sult

Qo Qnom Qult

FlowPCSE/hr

S4

Speed Flow Model

Road Type Width (m)

Qo/ Qult

Qnom/ Qult

Qult (PCSE/h/lane)

Sult (km/h)

Single Lane Road < 4.0 0.0 0.70 600 10 Intermediate Road 4.0 to 5.5 0.0 0.70 900 20 Two Lane Road 5.5 to 9.0 0.1 0.90 1400 25 Wide Two Lane Road 9.0 to 12.0 0.2 0.90 1600 30 Four Lane Road >12.0 0.4 0.95 2000 40

Qo = the flow below which traffic interactions are negligibleQnom = nominal capacityQult = ultimate capacity for stable flowSnom = speed at nominal capacity (0.85 * minimum free speed)Sult = speed at ultimate capacityS1, S2, S3…. = free flow speeds of different vehicle types

Speed-Flow Model Parameters by Road Type

Speed Flow Types

Speed (km/hr)

Flowveh/hr

Four Lane

Wide Two Lane

Two Lane

Roadside Friction

Congestion Modelling

Uncongested

Congested

0

Acceleration in m/s/s

Effects of Speed Fluctuations(Acceleration Noise)

Vehicle interaction due to:volume - capacity roadside frictionnon-motorised traffic road roughnessdriver behaviour & road geometry

Affects fuel consumption & operating costs

dFUEL Values by Acceleration Noise and Vehicle Speed

Vehicle Speed Acceleration Noice in m/s2Class (km/hr) 0.05 0.10 . . 0.70 0.75Car 10 0.0063 0.0701

15 0.0095 0.138620 0.0083 0.1813..

90 0.1092 0.195995 0.1133 0.1877

100 0.1255 0.1890Bus 10

1520.

Truck 1015.

Fuel Model

• Replaced HDM-III Brazil model with one based on ARRB ARFCOM model

• Predicts fuel use as function of power usage

TRACTIVE FORCESRolling, air, inertia, gradeand cornering resistance

ACCESSORIESCooling fan,

power steering,air conditioner,alternator, etc.

INTERNALENGINE

FRICTION

DRIVE - TRAININEFFICIENCIES

TOTAL POWER

ENGINE FUEL EFFICIENCY FACTOR

ESTIMATED FUEL CONSUMPTION

Parts and Labor Costs

• Usually largest single component of VOC

• Function of new vehicle price and maintenance labor cost

• Function of vehicle age (service life)

• Function of roughness

Capital Costs

• Comprised of depreciation and interest costs

• Depreciation based on a straight line depreciation function of the service life

• HDM-4 uses ‘Optimal Life’ method or constant service life method

• Optimal life method varies service life as a function of roughness

Roughness on Depreciation

0

1

2

3

4

5

6

7

0 5 10 15 20 25

Roughness in IRI m/km

Dep

reci

atio

n C

ost

in

Bah

t/km

.

PC LT MT

HT AT LB

MB HB MC

Road Safety

• HDM-4 does not predict accident rates

• User defines a series of “look-up tables” of accident rates

• The rates are broad, macro descriptions relating accidents to a particular set of road attributes– Fatal– Injury– Damage only

Accident Rates Examples

South Africa Gravel Road 2 Lane Paved Road

Economic Accidents 230.0 100% Accidents 100.0 100%

Evaluation w Fatality 25.0 11% w Fatality 8.0 8%

Manual w Injury 39.0 17% w Injury 27.0 27%

w Damage 166.0 72% w Damage 65.0 65%

Canada 2 Lane Paved Road 4 Lane Divided Expressway 4 Lane Freeway

British Columbia Accidents 121.0 100% Accidents 93.0 100% Accidents 50.0 100%

Economic w Fatality 1.9 2% w Fatality 1.1 1% w Fatality 0.5 1%

Evaluation w Injury 36.3 30% w Injury 30.0 32% w Injury 16.2 32%

Manual w Damage 82.8 68% w Damage 61.8 67% w Damage 33.4 67%

Number per 100 million vehicle-km

- South Africa: Economic Warrants for Surfacing Roads, 1989, SABITA and CSIR- Canada : The Economic Appraisal of Highway Investment “Guidebook”, 1992, Ministry of Transportation

Non-Motorised Transport

NMT User Costs and Benefits

• Travel speed and time• Wear and tear of some NMT

vehicles and components• Degree of conflicts with MT traffic• Accident rates• Energy consumption

Emissions Model

Estimate quantities of pollutants produced as a function of:– Road characteristics– Traffic

volume/congestion– Vehicle technology– Fuel consumption

– Hydrocarbon– Carbon

monoxide– Nitrous oxides– Sulphur dioxide– Carbon dioxide– Particulates– Lead

HDM Series – Volume 4