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Road User Effects. Rodrigo Archondo-Callao ETWTR. The World Bank. 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

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Road User Effects

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road user effects

Road User Effects

Rodrigo Archondo-CallaoETWTR

The World Bank

representative vehicles

Small Car

Medium Car

Large Car

Light Delivery Vehicle

Light Goods Vehicle

Four Wheel Drive

Light Truck

Medium Truck

Heavy Truck

Articulated Truck


Light Bus

Medium Bus

Heavy Bus




Animal Cart


Representative Vehicles


Non-Motorized Traffic

road user costs models
Road User Costs Models

Vehicle Operating Costs

  • Fuel
  • Lubricant oil
  • Tire wear
  • Crew time
  • Maintenance labor
  • Maintenance parts
  • Depreciation
  • Interest
  • Overheads
  • Passenger time
  • Cargo holding time

Time Costs

Accidents Costs

vehicle speed and physical quantities
Vehicle Speed and Physical Quantities

Road Roughness and Terrain and Vehicle Characteristics

Vehicle Speed

Unit Costs

Physical Quantities

Road User Costs

terrain characteristics rise plus fall and horizontal curvature
Terrain Characteristics: Rise Plus Fall and Horizontal Curvature

Vertical Profile

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

Horizontal Profile

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

physical quantities
Physical Quantities


Quantities per Vehicle-km



Lubricant oil


Tire wear

# of equivalent new tires

Crew time


Passenger time


Cargo holding time


Maintenance labor


Maintenance parts

% of new vehicle price


% of new vehicle price


% of new vehicle price

free flow speeds model
Free-Flow Speeds Model

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

  • 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 flow speed and gradient
Free-flow Speed and Gradient







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



Grade Resistance

Air Resistance

Rolling 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 is calculated as a function of roughness.


RI = Roughness

ARVMAX = Maximum average rectified velocitya0 = Regression coefficient


VDESIR 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 limit

ENFAC = Speed enforcement factor

VDESIR0 = Desired speed in the absence of posted speedlimitVDESIR0 = VDES * XFRI * XNMT * VDESMUL

XFRI, XNMT = Roadside and NMT factors

VDESMUL = Multiplication factor

VDES = Base desired speed

traffic flow periods
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.

Flow Periods



Next to Peak

Medium flow

Next to Low


Number of Hours in the Year

passenger car space equivalent pcse
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.

speed flow model
Speed Flow Model

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

Speed (km/hr)











speed flow model15
Speed Flow Model

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 Flow Types

Speed (km/hr)

Four Lane

Wide Two Lane

Two Lane



effects of speed fluctuations acceleration noise
Effects of Speed Fluctuations(Acceleration Noise)
  • Vehicle interaction due to:
    • volume - capacity
    • roadside friction
    • non-motorised traffic
    • road roughness
    • driver behaviour & road geometry
  • Affects fuel consumption & operating costs
fuel model
Fuel Model
  • Replaced HDM-III Brazil model with one based on ARRB ARFCOM model
  • Predicts fuel use as function of power usage
parts and labor costs
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
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
road safety
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
Accident Rates Examples

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

nmt user costs and benefits
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
Emissions Model
  • Hydrocarbon
  • Carbon monoxide
  • Nitrous oxides
  • Sulphur dioxide
  • Carbon dioxide
  • Particulates
  • Lead

Estimate quantities of pollutants produced as a function of:

  • Road characteristics
  • Traffic volume/congestion
  • Vehicle technology
  • Fuel consumption