Divided roads
The travel time savings if the speed limit were increased to 130 km/h on rural divided roads were estimated to be the same as on freeways, and the percentage change in crash costs would be similar. However the number of additional casualties would be higher because of the higher initial crash rate. Fatal crashes would increase by 3.4 per year per 100 km of divided road. Similar remarks regarding the economic analysis of rural divided roads apply as were made for freeways, except that a simple increase in the speed limit to 130 km/h would have a substantial economic cost ($6.45 million increase per year per 100 km of road). Even higher figures would be estimated with alternative valuations of leisure travel time and road trauma.
The economic loss on divided roads could be overcome to a large extent if trucks were limited to 100 km/h. However a variable speed limit system allowing speeds of 120 km/h under good conditions would not be as beneficial as on rural freeways. There would be an additional 0.3 fatal crashes per year per 100 km of road, but a saving of 2.5 minutes per car travelling over the 100 km section averaged over the whole day. A system allowing 130 km/h on divided rural roads during good conditions would result in greater road trauma levels.
Undivided roads
There is apparently no economic justification for increasing the speed limit to 130 km/h on the two-way undivided roads, especially the lower standard 7.0 m sealed roads without shoulder sealing.
On the straight undivided sections without intersections or towns, total costs on the 7.0 m roads would be increased by $2.04 million per annum per 100 km of road, or almost 10% of current costs. There would be travel time savings of 13.8 minutes per vehicle over 100 km, but an increase of 0.8 fatal crashes per year on the same road section. (The increase in casualty crash costs would be 142%, but the number of additional fatalities and casualties per 100 km road section would be lower than on divided roads because of the lower traffic volumes on typical undivided roads.)
On the lower standard undivided roads through curvy terrain requiring slowing and occasional towns requiring stopping, the average speed would be lower and the travel time savings would be only 9.8 minutes per vehicle over 100 km. The total cost associated with raising the speed limit, and hence the cruise speeds, to 130 km/h is estimated to be $14.78 million per annum per 100 km, due to increased fuel consumption predominantly and to increased air pollution emissions, each associated with the deceleration-acceleration required by slowing and stopping from 130 km/h cruise speed and returning to that speed.
The optimum cruise speed for cars travelling on these roads is estimated to be 100 km/h if the road is straight without crossroads and towns, but only 85 km/h if the road has many sharp bends and includes intersections and towns requiring stopping. The optimum cruise speed for trucks is estimated to be 85 km/h, and no more than 80 km/h on curvy undivided roads of the same standard. Optimum cruise speeds would be somewhat lower if ‘willingness to pay’ values were used for crash costs, or lower values were used for leisure time savings.
On the higher standard, 8.5 m shoulder-sealed undivided roads, an increase in the speed limit to 130 km/h would not result in as many additional crashes as on the lower standard roads, but the total cost would still increase by $1.02 million per annum per 100 km of straight road: about 5% of current total costs. The travel time savings would be the same as on the lower standard undivided roads, but on the straight sections without intersections or towns there would still be 0.5 additional fatal crashes per year per 100 km of road. These calculations assume equal traffic volumes on higher standard and lower standard undivided roads. In practice, traffic volumes are likely to be higher on the better roads, so the number of additional casualties and the net cost increase per section could be higher on these roads.
Again, as with the lower standard undivided roads, the higher standard roads through curvy terrain and passing through towns would experience substantial increases in total social costs associated with the increased speed limit, due to increased fuel consumption and emissions because of frequent deceleration and acceleration. The total cost associated with cruise speeds of 130 km/h on such roads would be $13.65 million per annum per 100 km of road. Travel time savings would be reduced compared with straight 8.5 m shoulder-sealed sections, and fatal crashes would be increased by 0.6 per year per 100 km of curvy road.
The optimum cruise speed for cars travelling on the higher standard undivided roads is estimated to be 105 km/h if the road is straight without crossroads and towns, but only 90 km/h if the road has many sharp bends and includes intersections and towns requiring stopping. The optimum cruise speed for trucks is estimated to be 90 km/h, but only 85 km/h on curvy undivided roads of the same standard.
The travel time savings if the speed limit were increased to 130 km/h on rural divided roads were estimated to be the same as on freeways, and the percentage change in crash costs would be similar. However the number of additional casualties would be higher because of the higher initial crash rate. Fatal crashes would increase by 3.4 per year per 100 km of divided road. Similar remarks regarding the economic analysis of rural divided roads apply as were made for freeways, except that a simple increase in the speed limit to 130 km/h would have a substantial economic cost ($6.45 million increase per year per 100 km of road). Even higher figures would be estimated with alternative valuations of leisure travel time and road trauma.
The economic loss on divided roads could be overcome to a large extent if trucks were limited to 100 km/h. However a variable speed limit system allowing speeds of 120 km/h under good conditions would not be as beneficial as on rural freeways. There would be an additional 0.3 fatal crashes per year per 100 km of road, but a saving of 2.5 minutes per car travelling over the 100 km section averaged over the whole day. A system allowing 130 km/h on divided rural roads during good conditions would result in greater road trauma levels.
Undivided roads
There is apparently no economic justification for increasing the speed limit to 130 km/h on the two-way undivided roads, especially the lower standard 7.0 m sealed roads without shoulder sealing.
On the straight undivided sections without intersections or towns, total costs on the 7.0 m roads would be increased by $2.04 million per annum per 100 km of road, or almost 10% of current costs. There would be travel time savings of 13.8 minutes per vehicle over 100 km, but an increase of 0.8 fatal crashes per year on the same road section. (The increase in casualty crash costs would be 142%, but the number of additional fatalities and casualties per 100 km road section would be lower than on divided roads because of the lower traffic volumes on typical undivided roads.)
On the lower standard undivided roads through curvy terrain requiring slowing and occasional towns requiring stopping, the average speed would be lower and the travel time savings would be only 9.8 minutes per vehicle over 100 km. The total cost associated with raising the speed limit, and hence the cruise speeds, to 130 km/h is estimated to be $14.78 million per annum per 100 km, due to increased fuel consumption predominantly and to increased air pollution emissions, each associated with the deceleration-acceleration required by slowing and stopping from 130 km/h cruise speed and returning to that speed.
The optimum cruise speed for cars travelling on these roads is estimated to be 100 km/h if the road is straight without crossroads and towns, but only 85 km/h if the road has many sharp bends and includes intersections and towns requiring stopping. The optimum cruise speed for trucks is estimated to be 85 km/h, and no more than 80 km/h on curvy undivided roads of the same standard. Optimum cruise speeds would be somewhat lower if ‘willingness to pay’ values were used for crash costs, or lower values were used for leisure time savings.
On the higher standard, 8.5 m shoulder-sealed undivided roads, an increase in the speed limit to 130 km/h would not result in as many additional crashes as on the lower standard roads, but the total cost would still increase by $1.02 million per annum per 100 km of straight road: about 5% of current total costs. The travel time savings would be the same as on the lower standard undivided roads, but on the straight sections without intersections or towns there would still be 0.5 additional fatal crashes per year per 100 km of road. These calculations assume equal traffic volumes on higher standard and lower standard undivided roads. In practice, traffic volumes are likely to be higher on the better roads, so the number of additional casualties and the net cost increase per section could be higher on these roads.
Again, as with the lower standard undivided roads, the higher standard roads through curvy terrain and passing through towns would experience substantial increases in total social costs associated with the increased speed limit, due to increased fuel consumption and emissions because of frequent deceleration and acceleration. The total cost associated with cruise speeds of 130 km/h on such roads would be $13.65 million per annum per 100 km of road. Travel time savings would be reduced compared with straight 8.5 m shoulder-sealed sections, and fatal crashes would be increased by 0.6 per year per 100 km of curvy road.
The optimum cruise speed for cars travelling on the higher standard undivided roads is estimated to be 105 km/h if the road is straight without crossroads and towns, but only 90 km/h if the road has many sharp bends and includes intersections and towns requiring stopping. The optimum cruise speed for trucks is estimated to be 90 km/h, but only 85 km/h on curvy undivided roads of the same standard.
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