Ngchen

With 4 to 3 road diets all the rage these days, I wonder how beneficial center turn lanes really are on less busy roads. Would a conversion (further road diet, ha ha) from 3 to 2 lanes, with BLs and only strategically located turn lanes (say at major intersections) be able to move traffic just as efficiently? Such conversion would require a minimum of land and money, and would make less busy high speed roads more bike friendly.

unterhausen

the main drag through my part of town has a center turn lane and 4 fairly narrow travel lanes. Speed limit is 40, I'm routinely passed by people going 60. My thought is that the width and openness of the road is contributing to dangerous levels of speeding and not doing anything to decrease traffic congestion. In fact, they have the lights timed to stop everyone 7 times before they get downtown, I assume this is a misguided traffic calming measure.

I would like to go to left turn lanes, one travel lane each way, and bike lanes. There is never a level of traffic that justifies 4 travel lanes. There probably was decades ago before the bypass was built around town. Now it just creates a no-man's land that isn't conducive to anything other than driving a motor vehicle.

To better address your question, I think the center lanes do encourage speeding. They should probably be replaced with left turn lanes and islands.

sggoodri

The amount of oncoming traffic (frequency of gaps) determines the average amount of delay to traffic behind a left-turning vehicle on a two-lane road without turn pockets. The number of turning vehicles multiplies this delay. If both of these numbers are small, the left turn lane does not add much in terms of performance.

Continuous center turn lanes have fallen out of favor on high speed roads with only one through lane in each direction, due to dangers caused when drivers move into it at high speed (e.g. to use it as a passing lane), not expecting oncoming traffic to move into it at the same time. Hence the term "suicide lane." The preferred low-volume high speed design is two lanes with turn pockets added at important intersections. At higher volumes, four lanes with a raised center median is preferred.

Before my company relocated, my daily bike commute included a couple of miles of 3-lane 45 mph posted road with 11' outside lanes and minimal shoulder. Drivers used part of the center lane to pass, without incident. Through traffic was busy but turning traffic was very light. The road was much more pleasant for cycling than similar roads with only two narrow lanes an no center lane.

Note that the 3-lane configuration without bike lanes does keep the right side of the roadway well swept by traffic, while still allowing space for drivers to pass bicyclists at generous distance by using the center lane. If a 2-lane with bike lane configuration is not frequently maintained by street sweepers (as would be the case on the high speed roads maintained by my state DOT) the bike lane would become less desirable to use, compelling me to ride on or near the bike lane stripe, and encouraging closer passing. If the bike lane were striped very frequently then it wouldn't be an issue.

Most DOTs prefer to add some sort of wide paved shoulder to new or improved rural high-speed two-lane roads to reduce crashes caused when drivers drop a wheel off the pavement, often overcorrecting to the left into oncoming traffic. These wide paved shoulders make cycling on two lane roads more pleasant in my opinion.

Lastly, if the bicyclist is the one who will be turning left, the three lane configuration is often preferable to two lanes, for the sake of getting out of the traffic stream while waiting to turn.

degnaw

I find that on a 2-lane road with a center turn lane, the turn lane has the same effect as a bike lane; drivers can pass a full lane to the left without necessarily waiting for oncoming traffic. This obviously brings up the suicide lane issue, but that's never been a problem to date.

wheel

I like the 5 or 3 lane configuration. The driver should be encouraged to move over into the center lane. 3 and 2 bike lanes.

Ngchen

Me too. I raise the question simply because it's expensive anytime new road has to be constructed, as opposed to altering the striping of existing roads. So it seems to me that at least under some circumstances, a 3 to 2 road diet that creates bike lanes would be a good conversion on high-speed, less trafficked roads.

Bekologist

except when the drivers refuse to use the center lane to pass and just honk and get angry instead. happened to me twice this winter so far.

I think space separate from the general traffic flow is a preferable treatment for bicyclists on higher speed corridors.

converting a two lane with center turn lane into a two lane with bikelanes and turn pockets for significant intersections sounds great for bicyclists needs. check out this rural highway design below. Like Steve mentions, it all depends on the level of traffic, turning traffic, delays and safety issues generally.

Oregon specifies in some way that all highways have widened shoulders added anytime road improvements are made so as to benefit bicyclists.