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Old 04-19-2019, 05:10 AM   #33 (permalink)
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Originally Posted by Vman455 View Post
If you're assuming 30% efficiency, it's closer to 120,000 for a rolling 1 mph stop to save one gallon, 60,000 for 2 mph, and so on (because K = 42.9% of Q, which is itself only 70% of total E). Even if you have 5 different stop signs on your commute, and roll through all of them consistently, that's only 1250 stops per year assuming a two week vacation, no other holidays, and a five-day work week. At 4 mph, that's a payback time to save one gallon of 12 years. Now, how many gallons could you buy for the cost of one ticket? And how many people are consistently and constantly rolling through every stop sign at 4 mph? If this is really a concern, I would take slowmover's advice and find a different route!
I'm not sure your formula checks out because if I plug in 64mph, it would take 1875 stops to save 1 gallon. At 128mph, it would take 940 stops to save 1 gallon. In reality I'd wager it would take about 1 gallon to get to 128mph just once.

I have ~22 lights (1 per km) on my commute and if I get a lot of reds I see around 30mpg, while my best is 51mpg (would no doubt still have had to stop a few times). Since I average 20mph I'd say my speed through lights that stay or change green isn't super high. But at 30 vs 50mpg it only takes 1 week to save a gallon. Theoretically, if I had all greens, I'd be looking at 62mpg (my stready state consumption at the speed limit), and all reds would be worse than 30mpg too.

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