You can (almost) legally coast in NH – but only under 15 mph

One of the oddest laws on the books in New Hampshire is one that makes it illegal to coast your car in neutral.  I wrote about the law last year but the story is currently stuck in limbo due to the Monitor’s transition to a new computer system, so I can’t link to it: Basically, it (and many similar laws around the country) were put in place because you have less control over your vehicle when coasting – you can’t speed up to avoid an accident if necessary – so it’s potentially unsafe.

The geekly interesting part of this issues is that most people (including me) coast because it seems to increase our gas mileage, but according to the studies I’ve seen coasting in neutral actually uses *more* gasoline than coasting in gear, even though your RPMs are less in neutral. The reason for this counter-intuitive results: When you’re in neutral, the engine is being turned over only by fuel being spritzed so the sparkplugs can fire, just as when you’re stopped in traffic. When you’re coasting in gear, however, much of the RPMs are being driven by the wheels turning, so less fuel is spritzed. Here’s how Popular Mechanics put it:

There is no fuel injected at all. Yes, the engine is turning over, the pistons are going up and down, the water pump, alternator and a/c compressor are working, so technically you can say the engine is running, sort of. But it’s not consuming any fuel. And that goes for automatic or manuals.

The law was targeted this legislative session as an example of unnecessary government overreach and I figured it was doomed – Coast Free Or Die. But weirdly, as I learned from Allie Morris roundup in the Monitor (read it here, about halfway down in the list), in the Senate the legal change was tweaked so that it only allows you to coast when you’re going less than 15 mph. (Here’s the bill so far.)

So I guess you can coast when pulling out of the driveway of stuck in stop-and-go traffic on a downhill slope, but pretty much nowhere else.

I understand the thinking behind that tweak, because when going faster the potential loss of control from being in neutral becomes dangerous, but that seems so complicated as to be pointless; better to just leave it completely illegal than to confuse people.

Because the Senate version is different than the House version, the two have to be reconciled – I think they duke it out in a cage match in the State house basement – before anything could go to the governor for her consideration. So don’t hold your breath.