Friday, January 13, 2012

Speed Kills, But So Do Speed Bumps

Traffic calming measures (road narrowing and s...Image via WikipediaUrban Traffic Calming and Health: A Literature Review ( 152 page pdf, Olivier Bellefleur & François Gagnon, National Collaborating Centre for Healthy Public Policy, Institut national de santé publique du Québec, Nov. 2011)

Today, the focus is on a report that reviews the literature on health aspects of traffic calming. Among several surprising points is that traffic calming is usually aimed at and has benefits related to reduced speed as a prime factor for injuries or fatalities from collisions. But many traffic calming techniques, such as speed humps, cause a variation in speed- a temporary slowing followed by rapid acceleration and THIS results in a doubling of vehicle emissions and lower air quality near the road. The message is to take both pollution impacts and speed impacts into consideration when implementing traffic calming.

Key Quotes:

“The effects of traffic-calming measures and strategies on the four health determinants considered in this review (number and severity of collisions, air quality, environmental noise, and active transportation) are usually conceived of as being linked – directly or indirectly – to the two main mechanisms of action associated with such measures, namely, the reduction of driving speeds and of traffic volumes at intervention sites”

“two main mechanisms of action to classify traffic-calming measures into two broad categories: those used to reduce driving speeds and those used to reduce traffic volumes”

“In urban environments, traffic is responsible for a significant portion of emissions of nitrogen oxides (NOx), carbon monoxides (CO), volatile organic compounds (VOCs) – including hydrocarbons (HC), and particulate matter (PM)…in Toronto, motor vehicles are responsible for 85% of CO, 69% of NOx and 16% of PM2.5”

“traffic-calming strategies can influence air pollutant emissions and ambient air quality by means of three main mechanisms:

Reduction of vehicle speeds- slowing down of traffic due to traffic calming strategies should be accompanied by an increase in emissions.. a decrease in driving speeds and more frequent speed variations following the interventions explain the increases observed

Reduction of speed variations- Frequently varying speed while driving thus tends to produce more air pollutant emissions than driving at a constant speed

Reduction of traffic volume- approximately 90% of air pollutants are emitted during the first 200 seconds that a car is in motion when travelling less than 6 km in a city”
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1 comment:

  1. Wow! There are way too many close calls and tragedies that could be prevented by drivers doing the right thing. Thanks for sharing your post!!
    Speed humps