Speed and environment; speed and travel time
Speed not only affects road safety, but also the environment such as
- The level of exhaust emissions
- The level of traffic noise
- Fuel consumption
- Quality of life for people living or working near the road.
In general, high speeds and large speed variation have a negative effect on each of these factors. High speeds and large speed variation also have a negative effect on road safety. Hence, with regard to speed management, road safety aims and environmental aims have much in common. Co-operation between road safety and environmental organisations may increase the political and public acceptability for speed management measures.
Speed also affects travel time. In principle, higher speeds result in a reduction of the travel time. However, higher speeds lead to more accidents and accidents are an important cause of congestion. In addition, in particular on short journeys, the perceived gain of time is much larger than the objective gain of time, which is in fact only marginal:
|
Original speed
|
50 km/h
|
70 km/h
|
90 km/h
|
110 m/h
|
130 km/h
|
|
Extra time taken (minutes)
|
1.33
|
0.66
|
0.39
|
0.26
|
0.18
|
Extra time taken for a 10 km journey when speed is reduced by 5 km/h (Source: ETSC, 1995)
| 
