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Thursday, July 2, 2009

Do American Highways Make the Grade?

During my recent travels to Germany, I was surprised and impressed by how much I enjoyed driving on the freeways. This past weekend, I realized exactly what it was that was so enjoyable about them. I drove a giant square from Laurel to Bethesda to Frederick and back to Laurel, on Interstates 95, 495, 270, and 70. I never thought I would say this, but our highways are under-engineered.

The A-6 in Germany above grade with an exit to an arterial road running at grade. Photo copyright David Murphy.

I drove through five different Western European countries on my recent business trip to Germany. The highways in all of them were straighter and flatter than our highways. Because of this, their footprints were much smaller, the lanes were not as wide, and their speed limits were much higher, if there was a limit at all. This placed much of the highway on bridges and in cuts, allowing for far less impact on the local road networks (which was already minimal because European freeways rarely run through cities like our interstates). The terrain of Germany, France, and the low countries is at least as hilly as Maryland's, so it was a very notable comparison between the grading of their freeways and ours.

Interstate 270 to Frederick is one of the straightest highways around DC, but after driving on the Autobahn it was very obvious that there are many more minor curves, and the road tightly hugs every elevation change along the way. The A-6 in Germany, by contrast, tended to remain flat through the dips and rises of the terrain. The sight lines were far greater; I could probably see at least a mile ahead at most points on the freeway. Speed limits were generally 100-130 km/h (62-81 mph) and most of Germany had no speed limit except around major interchanges. (Where Germany has speed limits, they are strictly enforced). Combined with laws prohibiting passing on the right and requiring slower cars to make way for faster cars coming up behind them, I saw little congestion on European highways, even during rush hour, even through construction sites.

On Sunday while driving down I-270 just south of Frederick, traffic slowed to about 20 mph for no apparent reason. Perhaps if this road had been properly graded when it was constructed, they would not be considering widening this stretch (pdf). Adding lanes will only generate more traffic (pdf) and make the bottleneck at the Beltway even bigger. Does this mean we should completely regrade I-270? Of course not. But it does mean that perhaps lack of lanes is not what is making traffic so annoying on 270.

Obviously, grading a highway this way is much more expensive. However, if it facilitates better traffic flow, in the long term it pays off. It pays off even faster when considering that the footprint of the highway will be significantly smaller. More even grading and straighter carriageways will also save fuel. Over time, this will add up to quite a bit of fuel. Perhaps it would help lower our per capita road deaths a little more. Right now the only thing decreasing our highway fatalities is the rising fuel costs. Instead, we allow new sub-par meandering freeways like the ICC wind their way through our rural landscapes without putting the structure into the infrastructure. It is no wonder traffic projections predict that the road will not alleviate traffic on any other area highways.

Am I saying we should tear up and rebuild all of our freeways in America? Absolutely not. But love them or hate them, freeways are the most important part of America's transportation infrastructure right now. Before the inevitable new highway is approved, it should be facing scrutiny over curves and small elevation changes like the ones on existing area highways. It could allow for better connectivity, more efficient land use, and it might even save fuel, money, and lives.

3 comments:

gavin said...

Is this a nationwide thing? The highways in, say, Florida are much more pleasant to drive than those in New York.

Dave Murphy said...

Arguably they are straighter and flatter in Florida, but in my experience their footprint is still far too wide. I-75 has its elevation changes, although since the terrain is less hilly they are less noticeable.

I would say Florida highways have less traffic, but I would not say they are pleasant to drive.

gavin said...

I said "more pleasant", not "pleasant" :)

See some of the newer highways in Florida -- 419 (the misnamed "GreeneWay" around Orlando) is pretty darn flat, with slow curves, long merge lanes, etc.