banking curves on exit ramps

[dstarfire]

there’s a curve on my daily commute that includes another street meeting this road mid-curve. This means the entire curve slopes down on the outside. Traffic slows from ~40mph (on the rest of the road, including a couple curves less than half a mile away) to 10-15 through that curve.

Banking has a big impact on speed people take through curves.

[ZurBob]

@jjakucyk

I’ve noticed more aggressive superelevation on older highways and ramps, especially

The most highly banked ramps I’ve experienced are the ones on the US-52/Business-40 cloverleaf in Winston-Salem, NC. The southbound 52 to eastbound 40 ramp is signed for just 15mph because it’s so tight. Being a traditional cloverleaf also means you have next to no time to accelerate back to highway speed because the ramps are so close together. Unfortunately Google Street View’s wide angle camera doesn’t do the slope justice.

Been through that interchange many times, and never noticed the drama you describe.

[jjakucyk]

@ZurBob

Been through that interchange many times, and never noticed the drama you describe.

Well, the problem with any cloverleaf that hasn’t been reengineered is the very short merging/weaving lane between the looped onramps and offramps. It’s worse in a smaller/tighter interchange because not only are the ramps closer together, but with lower ramp speeds you have even less time to slow down for the offramps or speed up to merge into the travel lanes.

[Novelty_Bobble]

They do this all the time, so much so that we don’t really notice it anymore.

Here’s a street view of the main M2-M25 slip roadas it curves around, you can see the slight camber and the drain holes on the right side of the carriageway confirms it.

In fact, sometimes when a contraflow is place during roadworks and the traffic has to be diverted over the central reservation, there will be a big flashing “adverse camber” sign because we are so used to the helpful camber that it can be unsettling when we experience the opposite.

[kenobi_65]

@wolfpup

I would certainly not say you can “easily double” the advisory limit, but you can certainly exceed it a lot most of the time, depending on the car and road conditions.

I had to take a traffic safety class a few years ago, after getting a speeding ticket. The class was taught by a former state trooper, who had also worked at a trucking company.

He noted to us that the posted speed for exit ramps was, generally, the maximum safe speed for vehicles that had a high center-of-gravity, and a relatively high likelihood of tipping over (i.e., trucks, buses, RVs). He stated that most cars (assuming good driving conditions and visibility, and a driver who knew what he or she was doing) would be safe on ramps at 15-20 mph above the posted speed.

That said, even though I drive a sporty car, and like to think that I know what I’m doing ;), I’ll treat an unfamiliar ramp with more caution than one that I’ve driven many times, and be far more respectful of that speed sign.