1. The current speed limits on freeway standard and other divided rural roads are 110 km/h for cars and light commercial vehicles (LCVs) and 100 km/h for all rigid and articulated trucks, and the speed limit on undivided rural roads is 100 km/h for all types of vehicle.
2. Vehicles of each type cruise at their speed limit, so that their average speed is the same as the limit, unless their speed is reduced by slowing for curves or stopping in some parts of the road section.
3. Apart from where indicated, the rural roads are relatively straight without intersections and towns, allowing vehicles to travel at cruise speed throughout the whole road section.
4. The mix of traffic by vehicle type is the same on each class of rural road, namely 67% passenger cars, 20% light commercial vehicles, 5% rigid trucks and 8% articulated trucks, and that this mix does not vary by time of day on rural freeways and other divided roads.
5. Crashes involving material damage only, and no personal injury, were not included in the analysis of crash changes with speed, and the likely increase in these crashes with increased speeds (albeit to a lesser extent than fatal and injury crashes) was not valued. Material damage crashes represented about 16.3% of total crash costs in Australia during 1996 (BTE 2000).
6. Scenarios in which truck speed limits are lower than light vehicle limits have been analysed on the assumption that the (increased) speed differential between these vehicle types does not in itself increase crash risk or the severity of the crash outcome.
7. The changes in speed limits are assumed not to increase or reduce travel demand and traffic flows of each vehicle type on the road sections.
8. The travel time savings on the rural road sections are of sufficient magnitude to be aggregated and valued.
9. The current economic valuations of travel time, road trauma, and air pollution emissions provide an appropriate basis for analysis which summates their values, together with vehicle operating costs, in a way which represents the total social costs of each speed. In other words, the current valuations are an appropriate basis for ‘trading off’ these tangible and intangible values of each impact. (Results for some alternative valuations are also presented).
10. Assessment scenarios involving variable speed limit systems do not include any estimates of capital and maintenance costs for the systems.
11. Illustrative traffic volumes used in the analysis were 20,000 vehicles per day for freeways, 15,000 for divided highways and 1,000 for undivided roads.
2. Vehicles of each type cruise at their speed limit, so that their average speed is the same as the limit, unless their speed is reduced by slowing for curves or stopping in some parts of the road section.
3. Apart from where indicated, the rural roads are relatively straight without intersections and towns, allowing vehicles to travel at cruise speed throughout the whole road section.
4. The mix of traffic by vehicle type is the same on each class of rural road, namely 67% passenger cars, 20% light commercial vehicles, 5% rigid trucks and 8% articulated trucks, and that this mix does not vary by time of day on rural freeways and other divided roads.
5. Crashes involving material damage only, and no personal injury, were not included in the analysis of crash changes with speed, and the likely increase in these crashes with increased speeds (albeit to a lesser extent than fatal and injury crashes) was not valued. Material damage crashes represented about 16.3% of total crash costs in Australia during 1996 (BTE 2000).
6. Scenarios in which truck speed limits are lower than light vehicle limits have been analysed on the assumption that the (increased) speed differential between these vehicle types does not in itself increase crash risk or the severity of the crash outcome.
7. The changes in speed limits are assumed not to increase or reduce travel demand and traffic flows of each vehicle type on the road sections.
8. The travel time savings on the rural road sections are of sufficient magnitude to be aggregated and valued.
9. The current economic valuations of travel time, road trauma, and air pollution emissions provide an appropriate basis for analysis which summates their values, together with vehicle operating costs, in a way which represents the total social costs of each speed. In other words, the current valuations are an appropriate basis for ‘trading off’ these tangible and intangible values of each impact. (Results for some alternative valuations are also presented).
10. Assessment scenarios involving variable speed limit systems do not include any estimates of capital and maintenance costs for the systems.
11. Illustrative traffic volumes used in the analysis were 20,000 vehicles per day for freeways, 15,000 for divided highways and 1,000 for undivided roads.
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