Science Forums 2

[TheBigDog]

Originally Posted by Boerseun

Heck. That must be US highway speeds, I guess. Over here, our highway limit is 120km/h in non-built up areas, and 60km/h in suburban areas. Consumption for most vehicles are best at around 80 to 85 km/h in high gear, which means your motor is ticking over very slowly. At legal limit, 120km/h, your car will almost use double per 100km what it would have at 80km/h, for 100km. This is due to higher revs burning more petrol and more stress on the engine due to increased wind resistance. So - quick solution would be for governments worldwide to lower highway limits.

Won't help you much with town driving, stop/start is a killer in anybody's books. But there's a lot of things you can still do, like taking your car out of gear when going downhill.

In 1974 Rep James J Howard (D-NJ) introduced the bill that changed the maximum highway speed limit to 55 mph. Because speed limits are not under federal authority they enforced this by withholding federal highway dollars from any state that did not comply with the mandated maximum speed. This was supposed to reduce gasoline consumption on the highways by about 17%. In the 90's this legislation was made void by a couple of congressional acts. Now the states set their own speed limits again.

For at least a short period of time there was an interstate in Montana with no daytime speed limit, and 75 MPH at night. Many of the western states have 75 MPH limits on the limited access interstates highways, but drop them to 65 MPH in commuter areas with higher traffic. Most eastern states have 65 MPH limits.

Nothing brought me greater joy than the day Interstate 195 in NJ got the speed limit posted to 65 MPH. The irony that the James J Howard memorial highway is not at 55 MPH is so sweet.

Bill