Do they use some kind of meticulous formulae and surveying instruments to decide when to begin and end no-passing zones? Are guys with calculators involved?
Or does the one driving the striping machine just go “Hmmph, can’t see over that hill yonder, better make this stripe solid”?
I drive a lot of County Highways now & it amazes me how well (someone?) anticipated a driver’s ability to see well enough to pass - and to complete a pass doing the legal speed before the next visual impediment arises.
Is this a summer job for civil engineers? Seems like either (a) somebody’s going to a lot of trouble recording these measurements precisely, or (b) they’re doing this intuitively & just happen to do it well.
It’s based on several factors, incuding (but not limited to) the speed limit on the road, the curvature of the road (both horizonal and vertical), if there’s an intersection ahead, and the length of highway between this No Passing zone and the next one.
Basically, these kinds of things will be figured out by surveying an existing road or determined during the design of a new roadway or roadway reconstruction. The engineers may decide to shave off the top few feet of a hill in order to level off the incline and reduce the length of a No Passing zone.
Here’s a link to the guidlines for No Passing zones in the state of Iowa. (PDF) I assume most other states follow similar guidelines.
Where I live they do an absolutely terrible job determining where it is safe to pass. You pretty much have to ignore the lines. Often, you can see well enough if it’s a solid line, and not at all in the so called safe to pass areas.
They tightened up the rules on the road between where I work and the nearest town. Now there are NO passing zones in the ~6 miles. It’s sometimes a PITA to get behind someone going 40MPH. The funny thing is those 40MPH people keep going 40MPH even when they hit the 35MPH speed limit at the town limits. They just have one speed.
I’ve passed on a solid line a few times when people were going 30-35MPH in a 55MPH zone. I don’t want to get rear-ended when someone pops up over a hill or around a curve behind me going 60. Wonder what the charge/penalty is for passing on a solid line (other than death if you do it wrong?)
I’d like to note that unless i’m traveling at least 40 miles an hour, I can’t be in 5th gear without risk of stalling. I like to be in 5th gear because otherwise I feel like i’m wasting gas. So, at least for some of us, breaking the speed limit in a slower area has to do with gearing issues.
This is my second post today that starts out with, “When I worked for the highway department, I took a course in…”
When I worked for the highway department, I took a course in highway design where they talked about how no-passing zones are set, and it’s supposed to be done by determining how far ahead you can see at a given point and whether or not you can pass safely when the coast is clear, given how far you would probably travel while passing someone.
So, yes, there are formulae and surveying instruments and people with calculators involved. I don’t know if they do it the same way everywhere, and I wouldn’t be surprised if it gets screwed up sometimes, but that’s how it’s supposed to happen in Texas.