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Yes except re fuel efficiency. My only negative re a blanket 20mph on all but through roads, is that it uses more fuel, as you never get into top gear. Most efficient fuel use is lowest revs at highest gear. I dont know the sums - if I have four gears and only use three, am I using 25% extra fuel?
OK on side roads you don't get above 20 anyway, but along eg StAnns, which as a non-red-route would be 20, cruising in third would waste fuel. Trying for 4th, I'd stall. Just sayin'.
Yes, and the more starting and stopping in heavy traffic the more fuel you use, too, so Green Lanes is worse for fuel consumption than a clearer road like St Anns.
I was taught (a while ago though) that petrol engines are most efficient at a steady 2000 to 2500 rpm, which corresponds to 40-50 mph in top (5th) gear, at least for a small car. That corresponds to about 25-30 mph in 3rd gear (at least for my car) and 14-18 mph in 2nd gear, so 20mph is beyond optimum efficiency what ever I do. One more reason to avoid getting out the car..... Just sayin'.
Gordon's right.
Fuel efficiency is not related to the gear you're in. It's all about the revs and the speed.
Doing 1750 rpm is much more efficient than 4000rpm.
As you go faster, the engine has to work against air resistance (drag). Drag is quadratic to the speed you're going, as you go faster, the air resistance goes up disproportionately (ie, need more power to stay at speed).
In the 20-30mph range, the biggest efficiency killer is stop-start traffic/lights. Acceleration really burns fuel, that's why cars with regenerative braking systems like the Prius are efficient as they can reclaim some of that loss.
St Ann's Road with its wide straight sections, assembly of local boy racers, Mercedes Benz owners club and pizza delivery bikes, and proximity to local hospital and park, would be perfect for a 20mph limit as a very minimum of traffic calming/ speed reducing measures.
I agree very strongly with this. St Anns Rd is a crucial route for cyclists wanting to get down to the canalside cycle paths, and I have more than once come close to getting sideswiped on my bike by cars who are going way over the speed limit. The fact that there are schools either on it or very close to it is another good reason to put a 20mph limit on it.
Nobody supports dangerous driving, but surely this is an argument for speed cameras not a 20mph limit? Are you saying that any road near a school, hospital or park should be restricted to 20mph?
I don't know every school or hospital or park location, but yes St Ann's Rd has all three, and would be suitable for 20mph limit. But I agree its long straight wide sections might be covered by speed camera, among other traffic calming measures, as a better way to encourage lower speeds.
I was accelerated at the other day when crossing at the junction of Black Boy Lane and St Ann's. Better crossings are required.
The crossing points around the roundabout at Chestnuts school are really nasty - you get a traffic island but nothing else, and many cars come around the corners very fast & seem to view young children as something to be ignored.
It's a puzzle that the school doesn't have safer crossing facilities over St Anne's Road & at that roundabout in general. There's some old flashing amber light signs up St Anne's road, but they aren't operational.
On the general 20 mph issue I reckon speed cameras & lots of fines would probably change culture - in the same way breathalysers helped deal with drink driving.
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