Speed Limits that are Literally Impossible to Follow

[vdeane]

Today I encountered an area where strictly following the speed limit is impossible.  There's a 30 mph zone on NY 787 (work zone, at least for now) directly adjacent to a 55 mph/minimum 40 zone.  Since you can't jump straight from 30 to 40 due to the mean value theorem, one must violate the speed limit at some point, either by going slower than the 40 minimum or faster than the 30.  Has something like this happened anywhere else?

[vdeane]

I presume the minimum wouldn't apply on acceleration/deceleration lanes, and at least it doesn't defy the laws of math (only physics and safety), but wow.

[roadman]

Having gotten their way with a citywide default 25 mph limit, the City of Boston is now proposing to drop the default citywide limit to 20 mph.

I hate it when ignorant politicians try to play traffic engineer by claiming "oh, but it'll be safer for everyone."

[seicer]

There is good reason for 20-25 MPH, notably for pedestrian (etc) safety and survivability. And the 20 MPH limit does not apply to every road in the city of Boston, so the overblown worry is overblown.

[jp the roadgeek]

I can think of a couple of places. One that comes to mind is on MD 281 as you come into Elkton from the east. Coming down a steep hill, the speed limit drops from 50 to 40 about 2/3 of the way down.  About a couple hundred feet later just before you get to a bridge, it drops to 25.  The hill has to be at least a 6 or 7 degree grade.  Unless you absolutely floor the brakes, it's impossible to go from 50 to 25 in that short a time.  The other is the Merritt Parkway.  The speed limit is either 50 or 55, but if you do anything under 65-70, you'll get run over. 

[1995hoo]

^^^^

I don't think the Merritt example, in particular, fits what vdeane was getting at because it's not "literally impossible"  to obey the speed limit on that road. Your own comment indicates that it's impossible as a practical matter, but it's not "literally"  impossible because you could absolutely set your cruise control at 50 or 55 and see what happens.

[Michael]

While driving on Milton Ave west of Syracuse a few times over the past year or so, I've noticed two "end XX speed limit" signs before a lower speed limit.  Those signs are used to indicate that the speed limit is now 55, so technically, the short distance between the first and second signs is 55.

Here's the first set of signs: 1 2 (279 feet apart)

And here's the second set: 1 2 (.1 mile apart)

[Hurricane Rex]

List in Oregon I refuse to follow:
ANY rural freeway/expressway of decent quality with a 55 mph speed limit (US 26, OR 22, OR 34 are the worst of them)
Interstate 5 in the Willamette Valley (the same speed limit as going over a mountain pass, which that should be 65)
Bend Parkway aka Bend expressway (45-65 jump is ridiculous on a freeway, let alone it being an expressway/freeway combo (I don't know if the south side of Bend fixed that yet or not))
25 mph speed limit on Ladd Hill Road in Sherwood (55 down to 25 with no warning on a downhill, impossible to brake in time once you see the 18x24 sign)
99W in Sherwood, especially considering a similar quality road 2 miles north is 55 mph (vs the 45 in Sherwood)

I know I'm stretching the question a little but you get my point. There are others I know I'm not mentioning but can't think of at the moment.

On the question 100%:
Any minimum speed limit during traffic congestion/rush hour.

[TheHighwayMan3561]

To answer the example in the OP though, overriding factors such as construction, traffic, or weather almost always mean the rules go out the window, so the work zone becomes an overriding circumstance and no laws are being broken.

[paulthemapguy]

List in Oregon I refuse to follow:
ANY rural freeway/expressway of decent quality with a 55 mph speed limit (US 26, OR 22, OR 34 are the worst of them)
Interstate 5 in the Willamette Valley (the same speed limit as going over a mountain pass, which that should be 65)
etc

^I drove US26 on the west side of the Portland metro a couple weeks ago.  A purely straight freeway with no grade crossings and low traffic, and a 55 mph speed limit.  Good god was that a stupid limit. 

[thenetwork]

Unless you've got a strong V-6 or V-8 engine, It is damned near impossible to hit 65 MPH on I-70 Eastbound going up Vail Pass in Colorado!!

Ditto for trying to hit 60 MPH further eastbound on the even steeper hill between Dillon & the Eisenhower Tunnel!!

[Mapmikey]

South Carolina used to be full of these as many towns posted a 30 mph limit adjacent to a 55 mph with either a 35 or 40 minimum. This may still be the case but S.C. doesn't post minimum plates on their speed limit signs like they used to.

One situation that used to scratch my head was US 64 east leaving Cashiers had a 55 mph limit back in the late 80s when it was so twisty that it wasn't possible.

[bzakharin]

According to NJ law drivers in free-flowing traffic in the left lane of a "highway" must remain "near" the posted speed limit at all times. Depending on the definition of "near" *any* speed limit change will make it impossible to remain in the left lane.

[roadman]

There is good reason for 20-25 MPH, notably for pedestrian (etc) safety and survivability. And the 20 MPH limit does not apply to every road in the city of Boston, so the overblown worry is overblown.

The current law is 25 unless otherwise posted, and the proposed 20 mph law will be the same.  Most streets in Downtown Boston, even major ones, are not currently posted - that's one of the reasons behind the current and proposed laws - the City of Boston is too lazy and cheap to do proper speed studies, so they strong arm "default' speed limit laws through the Legislature.  And in the recent events that triggered these changes, the drivers in question weren't going between 25 and 30, let alone between 20 and 30.

The fact remains that a reasonable limit (30) with proper enforcement would do far more for overall safety than setting an unreasonable limit does.

[seicer]

Not every street needs a traffic study. Those are expensive and in most cases, unnecessary. Let's be reasonable - it's downright impossible to even go 30 MPH on most roads in the inner city

A blanket limit is just fine and doesn't really make anyone's commutes worse and doesn't really impact travel times.

[hotdogPi]

Not every street needs a traffic study. Those are expensive and in most cases, unnecessary. Let's be reasonable - it's downright impossible to even go 30 MPH on most roads in the inner city

A blanket limit is just fine and doesn't really make anyone's commutes worse and doesn't really impact travel times.

Much of the Boston city limits is not "inner city".