Economic evaluation of road safety measures - Swov

6.3. Quantifying effects
Whether there is sufficient information available to quantify effects is
mainly determined by the packages being evaluated and the measures that
they include. It should be assumed that no research has been done into the
effectiveness of the packages put together for this goal, but certainly into a
number of the separate measures. The effectiveness of packages therefore
has to be assessed on the basis of expert judgement, using knowledge
about the effectiveness of individual measures. The distribution of effects
over time also has to be estimated in this way.
A complication is that many traffic safety measures are adopted whose
direct intended effects do not aim to reduce the risk or seriousness of an
accident. This reduction can be a, sometimes highly remote, indirect effect
of these measures. This is clear in the following overview of measures that
often appear in traffic safety programs:
- people-oriented measures like information, education, training,
legislation and enforcement. The direct intended effects consist of
certain changes in behaviour (fewer speeding violations, increased seat
belt use, changing the speed of approach at junctions, less driving under
the influence etc.) or a change in knowledge and attitudes (knowledge of
right of way regulations, taking broader risk margins when overtaking
etc.)
- infrastructural measures such as dividing the road network into
functional categories and bringing the design of each category into
accordance with its function (e.g. the design of junctions and
connections with side roads, the presence of safety constructions). The
direct intended effects in this case are usually a reduction in the risk of
accident (e.g. measures that inhibit speed) or the seriousness of an
accident (like a crash barrier)
- vehicle-oriented measures like legal requirements for construction and
maintenance (e.g. crushable zones, minimum tyre depth, periodic
testing) or the presence of safety features (e.g. speed limiters, automatic
switch for daytime running lights, seat belts, air bags). The direct
intended effects are also a reduction in the risk of accident or the
seriousness of one
- post-crash measures like faster alert systems (emergency telephones),
faster assistance (helicopter), trauma teams in hospitals. The direct
intended effect here is a reduction in the seriousness of the outcome of
accidents (timely stabilizing of a patient's condition, faster recovery,
fewer long-term consequences)
- facilitating measures such as the organization of traffic safety policy
(decentralization of responsibilities to lower management levels),
education and information to create the basis for new policy, gathering
knowledge (research, monitoring) and distributing existing knowledge
amongst professionals. The direct intended effects are more effective
and efficient policy management, support for new measures, increase in
scientific knowledge and insight, expanding the professional expertise of
people preparing policy.
To be able to conduct a CBA, the intended indirect effects of peopleoriented
and facilitating measures on safety will have to be estimated along
with their distribution over time. If it concerns second order effects, this is
likely to be successful; the relationship between behaviour and the risk of
SWOV Publication D-2000-16E 31