Influencing Busy Four-Lane Highway/Freeway Speeds to Increase FE
 

Is it just me, or does driving the speed limit help to reduce the risk of running into traffic jams? I feel like when it's busy on the Merritt / Wilbur Cross Parkway (a four-lane limited access highway, two lanes each way), if I just drive the speed limit of 55, cars have to slow down and get over to the left lane to pass me, so they kind of "trickle through". If I were to drive 65-70 like everyone else, everyone would kinda just be "pouring through" at a higher speed.

Eventually, this would lead to a bottleneck, because people would be merging on and off the highway and everyone would have to slow down to the speed limit or lower anyway. The way I do it, no one really has to slow down more than about 5 mph at any given time if someone merges on up ahead. So, does this idea of "influencing the speed of the road" ultimately help or hurt our fuel economy? Obviously this wouldn't work as well for roads with two passing lanes, but it seems like the basic idea deserves credence.

Its not just you.... it happens to me every day. Even if there is a decent amount of cars on the highway, you can actually do less than the speedlimit and bottlenecking will still occur. I like to refer to it as a slinky effect. People speed up as soon as they can best they think the speed limit is the minimum they should be doing, only to come to a complete stop again a mile down the road.

I find it really amusing how angry people get when they cant do atleast the speed limit, especially in rural areas where there is stop lights every half a mile. While i'm hypermiling in between lights, people behind me sometimes get instantly pissed off, some even hang their head out the window looking at me like i'm and idiot.... then i catch them at the red light, me coasting up to it. I just look over and give them a nod, with an ecomodder grin on my face.

Even if there was no traffic on the road, driving 55mph vs 65mph only costs me 10 minutes of driving just about. I'd rather get 10-15% better FE and drive 10 more minutes.

newhavenpatriot -

Here's someone who has a whole theory for it :

SCIENCE HOBBYIST: Traffic Waves, physics for bored commuters

CarloSW2

I know, I read that already! :D A lot of it kinda made sense, but then a lot of it also seemed really weird, too. I do agree with his basic premise that the closer together cars are, the slower the drivers go. The way I see "traffic theory", it's kind of like when you pour oil into a funnel or something. If you pour all of it in at once, it's gonna back up. If you pour it slower, everything will go through smoothly. If nothing else, I think allowing fewer cars to go by you quickly on the highway at least decreases the length of time you're stuck in traffic jams, even if encountering one is basically unavoidable due to the sheer volume of cars on the road at a given time. (see NYC-CT rush hour traffic)

Also, I think we (meaning state/federal government) could improve traffic flow greatly (but not cheaply) by making all exit ramps exit on both the left and the right. This would allow for fewer lane changes, which slow down traffic dramatically in high-volume situations. I don't envision putting offramps between lanes or anything like that, just because of the risk of running into the side of the offramp, but exits on both sides would help a lot, I think, especially on highways with two lanes in each direction.

newhavenpatriot -

Ok, you're wayyyyyy ahead of the game, :thumbup: . An interesting test of your observation would be to have a set of equally spaced right-lane-only speed-limit-only cars along a route. By what you write, this might keep the passing cars from ever getting "too fast" to cause a traffic jam.

CarloSW2

That's an awesome idea that I've actually thought about in the past, and I firmly believe it would work. I'd love to see the government/police/whoever hire "pace cars" to purposely get highway speeds down to the speed limit consistently along a very long stretch of road. This would create a ton of jobs for people, as well as improve safety and congestion on state highways. It would be bad for the environment because gas would be wasted from all those cars, but hey, I never said I cared about the environment. It might help the environment, though, because people might stay at a constant efficient speed, thereby reducing emissions from constantly braking and accelerating. I dunno...

Maybe we should have an ecomodder get-together to test this speed-limit-only theory... :)

That's actually how they manage highways with variable speed limits. Whenever there is something causing congestion, they lower the limit upstream so people do not come in rushing. It gives more time for the congestion to dissipate and keep a steadier traffic flow.

good theory but....

This only works when the "Others" smoothly merge around us. In my experience most drivers race up to my bumper, get mad, make an obscene gesture, pass wildly while making more gestures and cursing, and ultimately burning far more gas than I'm saving. This happens even when there are no cars in the passing lane to keep my gesturing friend from passing smoothly. Go figure?

Oh, I'm not worried about the jerks' mileage. They can go light themselves on fire, for all I care. I'm just theorizing that the more cars that work in tandem to reduce the flow of traffic down to the speed limit, the more those cars will enjoy less traffic jams down the road (assuming a road with one travel lane and one passing lane).