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Unintended consequences

Sometimes, policies in placed do not achieve their intended goals.  Instead of simply having no effect, a policy intended to make things better might make things even worse.

For example, late Dutch traffic engineer, Hans Monderman, famously maintained that many of our road regulations, designs and signs are counterproductive.  He believed that traffic efficiency and safety improved with minimized regulation. His studies determined that traffic and pedestrians moved quicker and safer when traffic engineering encouraged each person to negotiate their own movement among hazards and other drivers.

I sensed credibility to that premise when traffic lights in Spokane were inoperative for days during the 2015 wind storm.  When drivers were aware that there was no official traffic control at the intersections, everyone approached, stopped and passed through the crossroads with orderly ease.

Similarly, Monderman found that drivers faced with no prospect of warning signs were more diligently on the lookout for tight turns and other potential road hazards.  Officials in Australia recently considered raising speed limits there to improve safety.  They theorized that higher highway speeds would thwart driver drowsiness and increase attention levels. 

Whether or not safety would be improved or diminished with removal of signs, traffic lights and speed limits is a topic of debate.  However, a corresponding notion is recently being applied to the width of lanes for vehicle travel — a topic that has local relevance due to “road diet” proposals for Spokane’s Monroe Street and other regional locations.

A worldwide study by Subha Ranjan Banerjee and Ben Welle published at TheCityFix showed that cities with relatively narrow lanes had fewer traffic deaths per 100,000 residents.

Specifically, cities with lane widths of 9.2-10.6 feet, such as Amsterdam, Tokyo and Copenhagen, have the lowest traffic fatality rate (1.3-3.2 deaths per 100,000 residents), and cities with lane widths of 11.8 feet or more, like Beijing, have the highest fatality rate (15+ per 100K).

In the United States, where the lane width is commonly 10.6 to 11.8 feet, the fatality rate is about 10 per 100,000 residents.  Other cities around the globe with that lane width, such as New Delhi and Mumbai, have fatality rates of 7-11 per 100,000 residents. 

The 9.2-10.6 width seems optimum, since when lanes get narrower than 9.2 feet (Jakarta, Singapore), the fatality rate begins to rise (fatality rate of 3.6-6.4 per 100K there).

For years, traffic engineers have believed wider lanes to be safer by providing more maneuvering space and minimizing sideswipe accidents.  Yet, in an urban setting, wider lanes usually result in higher speeds with accompanying increases in crashes and injuries.

As for narrower lanes contributing to congestion, researchers point out that narrow lanes don’t stop traffic, but just slow it, and that a vehicle travelling at 20 miles per hour only takes a few more seconds to cover one mile than a vehicle travelling 30 mph.

The narrower lanes also improve safety for bicyclists and pedestrians as automobile speeds drop.  Pedestrians have a 90 percent chance of survival when struck by a vehicle travelling about 20 mph.  The survival chance drops dramatically with each mile per hour of increased speed.

So, these theories basically tout that driving can become safer by making it seem riskier to drivers.  When drivers perceive situations that are more difficult to negotiate, it appears that they respond by driving slower, with added attention and caution.

Readers may contact Bill Love via e-mail at precisiondriving@spokesman.com.

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