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Letter: Limiting speed, smart car choices improves mileage




To the editor:

The principal arguments for speed limits within the metro area remain those regarding safety. However, in a period characterized by gasoline prices ranging from $3 to $4 a gallon, it may be useful to consider a “pocketbook” argument for not exceeding those speed limits during “start/stop” driving in town.

Elementary physics considerations will clearly show that the energy expended in accelerating a vehicle from a stopped position to a given speed is directly proportional to the weight of the vehicle multiplied by the square of the achieved speed.

If, for example, in a 30 mph speed zone one accelerates from zero to 35 mph (easy to do), roughly 36 percent more energy (and fuel) will be required each time that happens. Pushing that speed further to 40 mph will require almost 80 percent more energy (and fuel). These numbers are far from trivial and over an extended period of in-city, start/stop driving, can truly impact the amount of money spent at the filling stations.

As a separate issue, the same laws of physics clearly argue for less weight in a vehicle. During in-city, start/stop driving, the 3,000-pound vehicle will always require twice as much fuel as the 1,500-pound vehicle regardless of how it is driven.

While we can do little to impact the complex market forces leading to high gasoline prices, we are free to make auto purchase and driving behavior decisions which can significantly mitigate the fuel cost (and environmental) impact of driving in our cities.

David A. Nealy

Greenwood

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