Do 20mph zones have a negative impact on the environment?

[David Mozer]

Optimum efficiency for all cars is not the same speed, it depends in part on
the gearing.  Noise and severity of accidents increase pretty directly with
speed.  Emissions are also a function of how warm the engine is and engines
continue to pollute after they are turned off.  It may be the case, if the
trips are short, that the speed limit may have little impact on the total
air pollution created for a trip.  In which case you might as well go for
quality of life.

-----Original Message-----
From: owner-sustran-discuss at jca.ax.apc.org
[mailto:owner-sustran-discuss at jca.ax.apc.org]On Behalf Of Knight, L V
Sent: Wednesday, March 08, 2000 5:28 AM
To: 'sustran-discuss at jca.ax.apc.org'
Subject: [sustran] Do 20mph zones have a negative impact on the
environment?


The UK Road Safety Strategy recently launched by the government stated that
an urban 20 mph speed limit would increase CO2 emissions and have a negative
effect on the environment.

In the next paragraph they gave support to self-enforcing 20mph zones in
urban areas especially around schools.  If anything I would think
self-enforcing 20mph zones where vehicles are forced to slow down and speed
up would not improve the quality of life for the immediate population, due
to noise and vehicle emissions.

However, it made me wonder if a balnket speed of 20mph would be detrimental
to the environment, does anybody know the answer or have any commnets about
20mph zones?