in Sweden? There is of course not a single correct answer to this question. The answer depends on the willingness to apply different measures. As far as traffic fatalities is concerned, the ten measures that have been estimated to have the greatest potentials are listed in table 20.
Measures that influence driving speed figure prominently on this list of measures.
Adopting Vision Zero speed limits, while keeping current road design would lead to a reduction of the speed limit from 90 to 70 km/h on most roads that currently have a speed limit of 90 km/h. On urban main streets, the speed limit would be reduced to 30 km/h at all crossing locations for pedestrians and cyclists. It has been assumed that speed enforcement would have to be drastically increased in order to enforce these quite drastic changes in speed limits. When estimating the effect of the measure, it was assumed that speed enforcement would be increased to ten times the current level. It was further assumed that mean speed would be identical to the posted speed limit. If driving speeds are normally distributed, this assumption implies that a compliance with the new speed limits of about 50% has been assumed. This is virtually the same level of compliance as currently. In other words: It was assumed that Vision Zero speed limits, if enforced more effectively than current speed limits, would command about the same respect as current speed limits. It was estimated that this measure, or rather combination of
measures, can reduce the number of fatalities by 307. This is more than 50% of the current number (assumed to be 554).
Table 20: The ten road safety measures that have the greatest potential for reducing the number of traffic accident fatalities in Sweden. First order effects. Effects cannot be added
Description of measure Potential reduction in the number
of traffic accident fatalities Adopting Vision Zero speed limits on all roads, keeping current road
design and increasing speed enforcement to ten times current level 307 Adopting Vision Zero speed limits, first reconstructing roads and
increasing speed enforcement to ten times current level 216 Adopting optimal speed limits on all roads and increasing speed
enforcement to five times current level 181 Requiring intelligent speed adaptation for all motor vehicles, without
changing current speed limits (perfect compliance) 181 Increasing enforcement of current speed limits to ten times current
level
133 Installing road lighting on all public roads 70 Reconstructing all main roads in urban areas according to the
design principles of 50/30 streets in Vision Zero 49 Requiring ignition interlock for seat belts in all cars (perfect
compliance) 37
Requiring a crash data recorder in all cars 35 Installing speed cameras (automatic enforcement) on about 12,000
km of road, speed limit 90 or 70 km/h
35
The price for safety in terms of reduced mobility if Vision Zero speed limits were to be introduced across the entire present road system would be substantial. The current strategy is to try to minimise the conflicts with other policy objective by reconstructing roads in order to allow a higher speed limit. If roads are first reconstructed according to the principles of Vision Zero, for example by providing median guard rails, by redesigning junctions or by providing raised pedestrian crossings, it would not be necessary to lower speed limits on all roads.
However, on many roads, lowering the speed limit would remain the most cost- effective option for improving safety. If roads are reconstructed to the extent that can now be envisioned, adoption of Vision Zero speed limits, combined with increased enforcement on the remaining road system could reduce the number of fatalities by 216. Thus, a consistent introduction of Vision Zero speed limits remains a very potent road safety measure.
Third on the list of measures that have a great potential for reducing the number of fatalities is the introduction of optimal speed limits. These are speed limits that minimise the total costs to society of travel. The total costs include accident costs, costs of travel time, vehicle operating costs and environmental costs. Optimal speed limits were estimated for a total of twelve categories of road, as shown in Table 21. Table 21 compares the speed limits according to three different speed limit systems:
1 The current speed limits 2 Optimal speed limits 3 Vision Zero speed limits
The latter have been assumed to be introduced to the current road system, without first reconstructing roads.
Table 21: Three different speed limit systems for public roads in Sweden. Speed limits and driving speed in km/h
Current driving speeds and three different speed limit systems for public roads in Sweden – kilometres per hour
Category Mean speed Current limits Optimal limits Vision Zero limits
Motorway 109 110 110 100 Motorway 97 90 100 90
Motorway 82 70 80 70
Motor traffic road 108 110 90 70
Motor traffic road 96 90 80 70
Motor traffic road 82 70 80 70
Rural highway 106 110 90 70
Rural highway 95 90 80 70
Rural highway 82 70 70 70
Urban street 66 70 60 70/50
Urban street 50 50 60 50/30
Urban street 39 30 60 30/7
It is seen that Vision Zero speed limits are the lowest. Optimal speed limits are in most cases lower than or identical to current speed limits. In a few cases, optimal speed limits are higher than current speed limits. In particular, optimal speed limits in urban areas are estimated to 60 km/h both for main streets and access streets with a current speed limit of 30 km/h. If these results were to be taken at face value, a substantial increase of the number of killed or injured road users in urban areas would result. As noted in section 6.9, there are reasons to believe that the current framework for cost-benefit analysis of traffic control measures in urban areas is inadequate and leaves out important elements, such as travel times for pedestrians and cyclists and the sense of security felt by road users and
residents along the road. The results for urban streets have therefore been rejected, and the current speed limit and current mean speed has been assumed to remain unchanged within a system of optimal speed limits.
When estimating the effects of optimal speed limits, it was assumed that
enforcement would be increased by a factor of five, and that the new speed limits would command a compliance of 50%. Given these assumptions, a reduction of 181 in the annual number of killed road users was estimated.
Ensuring perfect compliance with current speed limits comes close to giving the same safety benefit. It was estimated that if all motor vehicles have systems for
intelligent speed adaptation that ensure compliance with current speed limits, the number of fatalities would be reduced by 181.
It was judged that a similar effect cannot be attained by increasing conventional police enforcement. Based mainly on evidence from Swedish evaluation studies, it was estimated that the number of fatalities can be reduced by 133 by increasing the amount of speed enforcement by a factor of ten.
All these measures concern driving speed and the control of driving speed, which is clearly the most serious road safety problem in Sweden today. Sixth on the list of measures in Table 20 is providing road lighting on all public roads, which has the potential of reducing the number of fatalities by 70 per year. Reconstructing all urban main streets according to the design guidelines for 50/30 streets in Vision Zero can reduce the number of fatalities by 49 per year. The final three measures listed in Table 20 can each reduce the number of fatalities by about 35.
These measures include an ignition interlock device for seat belt wearing,
requiring a crash data recorder in all cars and installing speed cameras on selected roads. The estimate made for crash data recorders, in particular, is conservative, see the comments in section 11.1.