Speed is often given as the reason for safety problems and is one of the biggest factors in pushing road diets. The idea that you remove traffic lanes, and then traffic goes slower, is appealing, particularly for those that benefit from these lanes, often cyclists, but how does this work in practice, and what supporting evidence do we have?
Road diets only work to slow traffic using one of two methods:
- The cause congestion, so that traffic has to move slower since there is no lane to overtake
- They slow traffic since the person at the front of the traffic line is driving at or below the speed limit
If we examine the 2015 National Highway Traffic Safety Administration study regarding cyclists fatalities we see some interesting results:
We see that the weekend by far has the greatest number of fatalities and the hours between 3p.m and midnight are those with the greatest number. So, during the week-day commute hours, and light traffic periods in the daytime we do not see any significant difference in fatalities, but according to road-diet supporters, we should – since to be any benefit they need more traffic to cause slowing through congestion, or slower drivers.
What this data proves, is that road diets are not a consistently reliable solution to safety throughout the day, we need something better.
Another interesting set of data is the number of fatalities where alcohol was involved – the report shows “Alcohol involvement (BAC of .01 g/dL or higher) – either for a motor vehicle driver involved in a fatal pedalcyclist crash and/ or the fatally injured pedalcyclist – was reported in 37 percent of
the traffic crashes that resulted in pedalcyclist fatalities” – and road diets will not reduce this number.
So summarizing this data, we see that the reasons for using a road diet to improve safety by slowing traffic does not solve the primary causes of cyclist fatalities:
- During afternoon and weekend times when traffic is light, and congestion will not reduce speed
- By the involvement of alcohol in 37% of incidents