Interstate Highway System

On Sez You last night they posited an interesting factoid that while it sounds correct enough, has the sound of a UL. They stated that on the interstate highway system, one out of every five miles must be straight. The reason given was that in case of national emergency, the road could be used as an emergency runway. Can anybody either verify or give some sort of cite for this?

It’s an old urban legend, refuted in this Snopes page.

I hear they deliberately put curves on interstates every few miles to keep the drivers alert. If true, it might explain why some highways look like the straight portions were put in deliberately.

scr, I guess they ignored that rule when they built I-5 through Central California, I-10 west of Phoenix, I-70 across the Utah salt flats, and doubtlessly some highways in Kansas…serious highway hypnosis on those long flat stretches with nary a curve in sight.

Thanks! I thought as much. I’ve written the folks at the show through their website … we’ll see what happens.

My memory–and I’m having trouble finding an official confirmation–was that the earliest sections were built to be as straight as possible, (shortest didtance between two points, least engineering required, etc.), but that the later ones had the curves added to compensate for problems with the earlier ones.

On the one hand, they want to make interstates straight so they can be used as runways (they do this in Greece - I’ve seen freeways with markings for aircraft. But they’re paranoid). On the other hand, they want to put curves in to keep drivers alert (though cretinous billboards would be more remunerative, wouldn’t they). Surely, they just build interstates by the most direct route possible, allowing for topographic obstacles and land ownership problems.

However - a neat bit of trivia: it is said that the genius and arrogant Victorian engineer Isambard Kingdom Brunel designed the Great Western Railway’s mile-long Box Tunnel (going through a place called Box Hill in western England) to run at such an angle that the sun would shine straight through it at dawn on his birthday every year. Some say he miscalculated and the sun shines through it a few days later.

(see for more)

Either way, I would like to believe that mere mortal contemprary highway planners have better things to do than deliberately make bits of freeway straight or curved.

To avoid boredom on some of the French motorways large sculptures are placed at the side of the road every few miles and some of the over-bridges are painted in bright patterns and designs. They also tell you about every river and canel you cross and put up billboards showing the historical sites and products of the region you are passing through.

I just want to throw in my $0.02. Here in NY Metro area we have basically 2 sets of limited access roads. The 1st set was built back in the 20’s-40’s or around then and most are parkways due to low bridges. They are narrower and much more curvy then the more modern eisenhower interstates which are the 2nd set.

take out a map and compare these roads NY Thruway (newer) to the taconic parkway (older) running from NYC to Albany, LIE (newer) to the northern parkway (older). Rt 95 from the NYC line to CT (Newer) to the Hutch. River Pkwy (older). These are basically roads that run more or less along each other and go to the same places. The older roads have many more curves then the newer.

Part of the reason is because we are better of shapping the land (blowing canyons out of hills and putting a straight road in as opposed to running the road around the hill), Also I think for the old roads the gov’t was more inclined to loop the road around properties but now they just buy up the land and run it straight through.
And just a side issue - I hate the newer set of roads, they are just ugly, The parkways are much nicer to drive in my humble O

Interstates also followed the old highway system where convenient. Many of the Interstates follow older “US” routes, which were upgraded from two lane highway to limited access. In some cases, the older highway has to be maintained as a frontage road to allow local access, in others they got away with simply converting it, and saying that local jurisdictions had to figure out how to get local roads to the planned exits.

While I lived in CO, a large section of I-70 (through Eagle and so on) was still two lane highway. That stretch of I-70 followed US 6. IIRC, there was a flap about what completion of I-70 was going to do to access to some of the National Forest areas accessed by gravel road from the two lane highway, since the gravel roads were not going to rate exits.