Hypothetical situation:

[thebrokeenthusiast]

You're at a red light. In front of you is a couple of cars. Not far away from the red light is a popular place for people to turn into (coffee shop, wal-mart, whatever). You wait your two seconds, then start off, knowing that inevitably, one of these two cars will turn into that stop not far away. So, would it save more fuel to:

a) follow at the same speed as the car in front of you, knowing you'll have to brake then accelerate from a crawl (5-10 km/h), or...

b) drive a little bit slower than the other person (say, 35-40 km/h instead of 50 km/h), allowing more distance between you and the turning vehicle(s).

I know the difference isn't much, but that's the fun of the question.

[RningOnFumes]

Scenario two.

You won't be accelerating just to burn off the energy by braking. To save fuel, you'll need to conserve momentum. In the first case, you'll be burning useless energy in the initial braking.

[TrailDust]

Ditto...#2. If you gauge the distance correctly you can take your foot off the gas and coast, and not even have to tap your brakes. Save both gas and brakes that way. Driving a car is very similar to a boat or plane in that the best drivers are the ones who are best at energy management. Ask any fighter pilot.

[thebrokeenthusiast]

That's what I thought, but it's best to have someone confirm these sorts of things.

[gameguru1360]

or scenario 3...experiment by trying both scenario 1 & 2 and assess the results..

[RningOnFumes]

Well, Scenario 1 might work if you have a hybrid with regenerative braking abilities.

But what is that one rule of thermal dynamics which says you loose energy as you change from one form to the next? Think about it.. You gave gas energy for motion, then you're now taking motion and turning it into electricity.. in all cases, making abundant heat.

It's better to just conserve the momentum. IE Scenerio 2.

[Dave's]

I typically go with scenario #4- punch it and go around both cars.