Damn right op, going at 30 rather than 20 is a terrible thing to do. Driving at 20 is the moral choice. Yes it means your commute will be 50% longer than if you'd driven at 30, but that's a sacrifice we should all be willing to make, said no-one with a 2 hour daily commute.
You use twice as mich fuel to accelerate from 0 to 30mph as 0 to 20mph, and if you hit a pedestrian at 30mph there's a 20% chance it will be fatal Vs 2.5% at 20mph.
You are never going to average the speed limits throughout your drive, unless you're speeding. In an urban environment, where 20mph speed limits are used, you will lose seconds on your journey.
But anyway, where is this coming from? The post is about speed cameras, not what the limits are set to. Why are you even bringing that up?
Except it won't be 50% longer, not unless you're going cross country. If you're driving anything less than 100+ MI =,10 mph isn't going to make pretty much any difference in your commute time at all. Not to mention your just going to hit a light and someone traveling the actual speed limit will then pull up right along side you while you wait
That's the point yes, looking purely at math assuming a completely 100% clear no stop Journey it would be faster. But that's not how life works, you stop at lights, you slow down at ramps, you stop at intersections. All of these things together make it so that unless you're traveling like a hundred miles or more it's just not going to make a difference. I very regularly make trips between Seattle and Portland, the difference between trying to cruise control 65 the whole way and trying to cruise control 75 the whole way isn't very large. Last time I remember trying I think it was about a 20 minute difference in a trip that is almost 3 hours Real world slowdowns end up equalizing much of the journey
As someone who commuted an hour each way for a year, I both calculated to the best of my ability and then tested. I could shave 5 minutes off by going 65 instead of 55 on the 55 mph highways, and fuel consumption was significantly higher. Going 30 in a 20 zone will do jack shit for someone commuting on surface streets