Traffic safety: how drivers should use center turn lanes

By Doug Dahl

Q: Is it legal to use the center turn lane as an on-ramp to merge into traffic?

A: Yes, it is. I’ll get to the legal reference in a moment, but first let’s think about what that means. Drivers traveling in both directions on a roadway can legally use the center turn lane to both leave and enter that road. And the only thing that stops four different drivers from using all four of those approaches at the same time is their observational skills and understanding of the law. That sounds like a recipe for disaster, doesn’t it?

Maybe the Federal Highway Administration thought so too, because about ten years ago they decided to study center turn lanes (or as the folks in the road engineering business call them, two-way left turn lanes, or TWLTLs). As it turns out, the results of the study show that TWLTLs are an effective approach to reducing head-on and rear-end crashes, especially on rural roads.

Remember a time when you needed to make a left turn into a driveway and had to come to a complete stop to wait for a break in oncoming traffic. How nervous did you get thinking about a car coming up behind you at speed and not realizing you were stopped? That’s one of the benefits of the TWLTL – it gets you out of the lane of travel while you’re waiting to make a turn. They also help drivers who are making a left turn onto the roadway by allowing them to navigate only one lane of travel at a time. When pulling from a driveway onto the road, a driver waits for a gap in traffic coming from the left and pulls into the TWLTL. Then the driver waits for a gap in traffic in the lane they want to enter and pulls in.

I like that the original question described the TWLTL as an onramp for merging into traffic, because that’s a good way to think of it. The TWLTL gives you an opportunity to match the speed of the lane you’re entering before mixing with other cars. Without a TWLTL, the difference between vehicles pulling into a lane and those already there can be pretty huge, especially on some higher-speed rural roads. If you pull into the roadway at maybe 15 mph or so and then try to get up to speed, a car doing the speed limit on a 55 mph road is initially closing in at 40 mph; that’s like encountering someone driving 30 mph on I-5 (or 20 mph in the urban areas). It’s no surprise then, that even with the potential for the four simultaneous scenarios I described in the first paragraph, TWLTLs have reduced crashes on rural roads by 50 percent or more in some locations.

I started by stating that it’s legal to use the center lane to enter into the roadway; to verify that I’m not just making thing up, here’s the language in the law: “A two-way left turn lane is near the center of the roadway set aside for the use by vehicles making left turn lanes in either direction from or into the roadway.” In addition, the law states that the TWLTL is not to be used as a passing lane and that it’s illegal to travel more than 300 feet in the TWLTL. That middle lane isn’t a short cut to get around pokey drivers or traffic delays. The law also states that drivers are required to use their turn signals when using the TWLTL. That’s sort of redundant, since there’s already a law that demands that drivers are to use turn signals whenever moving right or left on a roadway, but giving the lack of turn signal use that I and many of you have lamented about, it’s a good reminder.

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