Comment of the Day: How Two Wrongs and a Right Make a Faster Left

COMMENT OF THE DAY: HOW TWO WRONGS AND A RIGHT MAKE A FASTER LEFT Traffic“There are ways to speed up intersections which are scientifically proven and sound but rarely implemented. One way to reduce accidents, improve traffic flow, and decrease left turn times is to prohibit left-hand turns altogether. Left-hand turns would be completed by driving through the intersection and making a u-turn before the next intersection, followed by a right-hand turn. The same lanes would flow faster, and more traffic could be carried with no increase in infrastructure. Left turn times are actually decreased by this method, which seems counter-intuitive. Traffic engineers recognize this, but neighborhood activists and politicians frequently oppose it as being inconvenient for drivers. . . .” [Jardinero1, commenting on Comment of the Day: A Different Approach to the Future of Downtown Approaches] Illustration: Lulu

11 Comment

  • Blocking left hand turns just causes congestion past the light. Look at shepherd and westheimer. They have blocked left turns all down that street leading up to westheimer and it’s basically a traffic nightmare (well, it was before the construction and we’ll see how it turns out).

  • Completely agreed with this. Just look at the “superstreet” in northside San Antonio on 281. Rigorously opposed when the design came out but has cut down on the traffic in this growing part of town significantly. Same design is being phased in on 71 outside of Austin. Fantastic way to cost effectively increase traffic flow.

  • If people allowed a bit of space between themselves and the vehicle ahead of them and let other drivers merge right to get around those making a left turn, Shepherd would flow pretty nicely. I think it’s more of a driver behavior thing than a poor road design.

  • I could agree with this, except it usually involves making a left turn into a neighborhood past the intersection (most major streets with significant traffic do not allow for u-turns anywhere close to the intersection, if anywhere at all) and then driving through the hood to re-connect As such, neighborhoods don’t oppose it as being inconvenient for drivers, but as being dangerous in intentionally pushing traffic flow onto residential streets not designed for high speed throughput and where the risk for pedestrians is greatly multiplied.
    While something of this nature could be addressed in some major thoroughfares, it’s rarely the major issue at hand and I would highly question spending funds for retrofitting roads. Best to save the funds to address other primary issues for traffic flow.

  • I agree with the premise that left-hand turns slow down traffic. Even with a median, many drivers leave their car butts hanging out in the traffic flow lane which effectively closes that lane. (They don’t realize that they really have enough space in front of them to allow their back half to clear the lane.)
    Given all of that, I avoid making a left-turn at uncontrolled intersections (e.g. those without a protected left signal) since there are too many “wacko bird” drivers to worry about in the opposite flow and behind me.
    An alternative is to just make 3 right-hand turns: it takes more effort but is less anxiety-producing and avoids blocking any lanes of flowing traffic. Sometimes, I think it takes less time to do this than to wait for enough traffic clearance to make a left-hand turn.

  • It is not just left hand turns, it is right hand turns as well especially downtown. This is the first city I have lived in where the pedestrian light signals to cross at the very same time drivers are given the green light to drive forward or turn. This backs up traffic for drivers waiting for pedestrians to cross before turning right which also backs up those trying to change lanes in order to turn and so on. It is especially dangerous when the far most right lane must take a right turn and the second most right lane can either drive forward or turn right. I have seen so many close calls as the driver in the second right lane does not see a pedestrian blocked by the driver in the far most right lane. In the cities I have lived in or visited, pedestrians get their signal to cross before traffic begins to flow.

  • These were called Michigan lefts and were common in the Detroit suburbs before I moved here a couple decades ago. I miss them. Most intersections equipped this way allow two way traffic at the signals. Here most lights allow only one direction at a time, meaning 4 signal changes to clear an intersection. There’s no way that can be more efficient. Still, I vote for more roundabouts first.

  • I’m with Dave – also a Michigan transplant. Half the comments here don’t seem to quite understand the concept. It’s a dedicated U-turn lane, so you no longer back up traffic. On busy roads, this U-turn then has light as well. Basically pauses the oncoming traffic so they can complete the turn. Since the next light for the oncoming traffic (~300′) is also red, it’s not delaying the oncoming traffic, just stopping them a little early. (While U-turn light is green, cross traffic has the green) The lights are synchronized… so what you end up with is basically eliminating the time needed for a left-turn light.

    No turns on to side roads (neighborhoods) needed. U-turn lane is dedicated, so no one lane is blocked like in the median left turns.

    I was never a fan of the ‘Michigan Left’ – but after being here for almost 15 years… I now see the benefits. There would be a cost of additional space needed (won’t work everywhere). At least for Houston ‘burbs it would work.

    First choice is also for roundabouts. Not only are they efficient, but they’re a hell of a lot of fun when empty and on a motorcycle!

  • @D, thanks for clarifying. A designated u-turn lane could certainly be a good idea in some areas. Interesting. Our city traffic planners will never do this, though. They are a pretty inept bunch

  • I can not agree. Lived in Jakarta Indonesia for several years where the traffic system was based on the u-turn. It was horrific. If the butt of the car wasn’t hanging out to block traffic behind, the nose was sticking out into on coming traffic. Peril loomed everywhere. In AU roundabouts are used effectively and I grew to wish we had implemented them in the US years ago. I expect the learning curve would be too steep at this point. Though in the Energy Corridor with all the expats we might have a shot.

  • As already mentioned (“Michigan lefts”), I first experienced this in Birmingham, MI. My gut reaction was that this was annoying and inefficient. I didn’t get to use them enough to really see the value.
    I am for roundabouts in Houston. We should put a lot more in. The Westcott one has worked well for me for several years. The Main St. one is designed opposite and messed things up. Streets like Shepherd should not all left turns at all. I’d prefer Shepherd to be one-way and to take another road and make it one-way in the opposite direction.