Thursday, December 01, 2005


Save Gas: Avoid Brakes!

All I have to say about the 55mph speed limit is "dumb". It's not worth the effort and may waste energy in the long-run. For one, people's time, and the time of the truck drivers that supply us with, well, everything, is worth a lot more than the fuel we'd save.

If you want to save fuel, at least 20% and maybe much more, avoid using your brakes. Every deceleration is matched by a corresponding acceleration. That wastes fuel. And if you come to a stop, you waste a lot more fuel. According to Pakistan Energy and Environment Management Center, a car coming to a complete stop can use 6 times the fuel of a rolling stop.

Below are three behaviors that I believe would cut down on fuel consumption if enough drivers buy in.

1. Accelerate Faster!
2. Obey the speed limit on surface streets.
3. Use your horn! Communicate.

The variation in speed and driving style causes traffic. Reducing variation will cut down on traffic and reduce both drive times and the frequency of fuel wasting stop/starts. Accelerating faster prevents backups from forming and lowers the number of cars that will have to stop as they join the flow of traffic. It also moves more cars through the queue faster once traffic has formed [that means less stops]. To accelerate faster, Dr. Mark S. Dougherty, a professor at Dalarna University in Borlange, Sweden who is involved in fuel-saving research, found that the best way is to use about two-thirds of available power and change through the gears relatively quickly [Next time you’re at the front at a traffic stop, try this. The space between you and the following car is how many more cars can be passing through every traffic signal. That’s a lot of fuel. Now multiply that by the number of cars that accelerate too slowly.]

Obeying speed limits allows for better planning of traffic light timing and better use of speed limit planning. The road system determines the average speed of your journey far more than your top speed while driving. It’s the intersections and turns that affect you average speed and drive time the most. Allow yourself to slow down to avoid stops. Accelerate Faster and Drive Slower. Result: shorter driving times, and less stops.

On one occasion, I drove north on Rochester Road here in SE Michigan. When the light turned green and the car in front of me didn’t quickly accelerate, I gave my horn a friendly tap. Often the cars would accelerate slowly, exceed the speed limit, and the slam on the brakes at the next light. When I could get around such drivers, I would accelerate quickly to the speed limit, or slightly below, and cruise. The cars would eventually speed passed me. Because they would queue up at the light and take their time accelerating, I would have to stop despite the light being green for several seconds. I, again, would tap my horn and accelerate quickly to the speed limit. The drivers started catching on, and we all began smoothly cruising through several traffic lights at a time.

While this instance was special because of the small/moderate number of cars in our traffic pocket, it is much more difficult to communicate/model smooth driving behavior if there is a large queue, slowly dispersing at a green light when you arrive. There is too much in view [too much to be aware] for drivers to analyze your driving or care about one car honking its horn. However, if several cars used their horns and modeled smooth driving behavior, I think it would drive the message home.

I am confident that an effort to coordinate speed limits and traffic light timing along roads in any community, and switching as many Stop signs to Yield signs as possible, follow by a large campaign to promoted smooth driving, focusing on the three simple behaviors I listed above, will have surprisingly beneficial effect on fuel consumption and reduce drive times.

This would have the added benefit of making drunk drivers easier to spot.

I think cabs that double as a delivery service in metro areas would also be a good idea.

Update: Welcome Chicagoboyz.

Update II: I've also noticed electronic speed limit signs in some communities. I see potential for networking these signs and traffic lights so that the postings vary. Speed posting could tell drivers what speed to drive to avoid hitting the upcoming traffic lights! Same could be done with GPS systems.

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