Things you think about driving in Seattle

June 17, 2008 9:16 AM

Why don't they shift freeway lanes to even out the wear?

If you're driving on a well-used freeway, the wear creates a pretty consistent striped pattern: unworn lane divider, worn left-tire area, unworn area under the car, worn right tire area, unworn lane divider, etc. So if they shifted the lanes over by 1/4, everyone's tires would line up nicely with the unworn patches of road. I know this isn't a new idea because some jackass has tried to patent it, but I've never seen it done. Why not?

posted by bjrubble to travel & transportation (12 comments total)

That isn't really wear that affects the roadway. The roadway will typically crack to pieces before car or truck tires will wear it noticably.
posted by JJ86 at 9:25 AM on June 17, 2008 [1 favorite has favorites]

This should not happen on a well-paved road, meaning one with a proper foundation under the road. So it's only a stopgap solution for roads that ought to undergo full-depth reconstruction.
posted by beagle at 9:25 AM on June 17, 2008

One other thing that might not be obvious is that moving a lane over is not just a matter of repainting, there are also usually physical markers like rumble strips and reflectors that mark the lanes. I don't know much about road construction but I'm guessing those things are not easy to move.
posted by burnmp3s at 9:32 AM on June 17, 2008

Also with concrete roads, the placement of the joint between sections of pavement is aligned to coincide with the lane marking. This helps in dark, rainy weather when lane markings are more difficult to see. Many times the lane markings wear away within a few years and drivers must drive by the location of the joint lines.
posted by JJ86 at 9:40 AM on June 17, 2008

There's an asphalt two lane highway near me that has grooves where your tires should go (I suspect not because of wear and tear but because of frost heaves). It's dangerous to drive on the raised parts because it throws your alignment off. If you're going too fast you'd better hold the steering wheel tight.
posted by desjardins at 9:55 AM on June 17, 2008

A few years back on route 78 in NJ, they were closing off lanes nightly near Berekley Heights to shave the middle of the highway down and make it even with the grooves.
posted by Mach5 at 10:02 AM on June 17, 2008

The grooves most likely are traffic road wear. The most likely cause of which is heavy trucks. In the UK some years ago, all large commercial vehicles had to be fitted with air suspension because of the damage they do to the roads with such weight on conventional suspension.

Trucks (especially ones that travel so heavy on poor roads with standard suspension) are incredibly bad on road wear. You tend to notice this more in the slower lanes and less in the faster (trucks aren't allowed there). I was quite surprised, on moving across the Atlantic, that conventional suspension was still being used as the thumping they give the road is pretty severe. American roads are pretty poor quality, from what I am used to, but there is a hell of a lot more of it, so maybe that's all par for the course.

As for moving the lanes over a bit, all the various ramps and road structure is designed around the existing layout and may not transfer too well. The amount of time, disruption and labour involved in moving all the lanes over is probably too expensive to do for a small advantage. Besides, the grooves would still be there for traffic going across lanes, and so still a hazard. If they are going to go to all that hassle (repainting lanes, etc) they may as well do the job properly, would be my guess.
posted by Brockles at 11:11 AM on June 17, 2008

It's also hard to erase the old lines completely. The 10 freeway in Los Angeles has had several lanes & shoulders added over the past few years and so the lanes have been shifted back and forth by several feet multiple times. When the sun hits the road, you can see "ghost lines" of paint and "ghost lines" of tire wear. These make it look like the 6-lane road has about 10 lanes which cross each other and merge randomly.

I can confirm it is terrifying the first time you drive it and you can't tell which lane paint or tire marks to follow!
posted by holyrood at 11:19 AM on June 17, 2008

I know that on many roads the "wear" pattern is really where the soot from exhaust and oil or grease from cars has not built up due to the constant tire taffic that doesn't allow it to build up. It's not so much the road wearing away as the travel areas being "cleaner". In this case, perhaps it would be easier to clean the roads than move the lines.
posted by qwip at 12:27 PM on June 17, 2008

My wife says it would cost more to reconstruct a shoulder (which isn't typically built to handle constant traffic) than it would be to repave. And if you're shifting everything over you'd end up on the shoulder.

Some shoulders are built with a "hard" foundation and could handle the traffic. But if you're eating into the shoulder you'll interfere with people's ability to pull over and get out of traffic.

My wife is a transportation engineer (for WSDOT!), so I'm paraphrasing here.
posted by O9scar at 7:53 PM on June 17, 2008

Highways has been doing this in stretches of the mountain parks of BC/Alberta (I don't know if it's to extend life or if there is another goal). It can be very confusing during rain at night similar to holyrood's experience in California.
posted by Mitheral at 9:06 PM on June 17, 2008

Thanks for the thoughtful responses. A few thoughts, if anyone is still reading:

* You would only have to shift lanes by 1/4 -- maybe 2-3 feet. It seems like this should have minimal impact on shoulder use.

* The "wear" is definitely wear -- in Seattle at least, many of the freeways feel like driving on cobblestones if your tires are in the tracks. Driving at the edge of the lane makes a huge difference.

* While many (most?) roads have seams coinciding with the lanes, I've seen a number that don't. This was one thing I started looking at when this question came into my head.

I suspect the real reason is a combination of what JJ86 and O9scar said -- it wouldn't affect the lifetime of the road, and it would be expensive. And driver comfort doesn't appear as a line item in the DOT's budget planning.
posted by bjrubble at 8:39 AM on June 18, 2008