Straight and left from left lane; right lane right turn only - why?

[wphiii]

In my city there are a few intersections, such as this one, where the road breaks into two lanes approaching the signal, and both continuing-straight and left-turning traffic are directed to use the left lane, while the right lane becomes right-turn only. I can't fathom why the lanes are configured this way, especially since there's no protected left turn, meaning that anyone who wants to keep going straight has to wait behind anyone who might want to turn left, which isn't easy to do because there's often a steady stream of traffic coming from the other direction. Heck, at certain times of day, it can sometimes only be possible for one car to make a left turn there during a green light, and only by waiting until the very end of the cycle. As it stands, people will often (technically illegally) use the right lane to go around left-turning vehicles anyway.

What am I missing? Is there a good traffic engineering reason why keeping-straight and right-turning traffic can't share the right lane?

[agentsteel53]

my guess: the engineers decided there were lots of pedestrians holding up the right-turn lane.

[wphiii]

my guess: the engineers decided there were lots of pedestrians holding up the right-turn lane.

That makes as much sense as anything, though there is an all-red pedestrian WALK phase available, which definitely cuts down on the amount of people who will try to cross outside of that phase. Unless it's purely a pedestrian safety issue, it still can't be nearly the hold-up that waiting for cars to make that left often is.

[Jardine]

Governor's office have an issue with local authorities ??

[getemngo]

Sault Ste. Marie is like this - nearly all signalized intersections (except where BS I-75 is 5 lanes) are set up this way. The pedestrian theory is a decent one, but I've thought of another: Not having a dedicated left turn lane allows more room for parking.

Notice how the parking lanes start almost immediately on the other side of the intersection. There's two ways you could put in a left turn lane here. One, have it in the center, which eliminates parking on both sides for the length of the turn lane. Two, give thru and right-turning traffic the right lane as wphiii said. This means through traffic has to unexpectedly switch to the right lane, then swerve back in the middle of the intersection. Easy in a car, but trucks might not be able to do that safely.

With a dedicated right turn lane, you only lose parking on the right side of the street approaching the intersection.

[jeffandnicole]

A more rural intersection near me is like this.  Main reason is that very few people are turning left.  Most people are going straight or turning right.  So it's better to split up the volume of traffic between the two lanes, rather than putting everyone in the right lane and leaving a left turn lane barely used.  It also allows traffic to turn right on red without being stuck behind someone going straight.

Also in regards to the OP's GSV: Traffic going straight in the left lane continues straight.  Traffic in the right lane would have to swerve to get back to the left.  While this condition does exist at countless intersections throughout the country, it's not the optimal setup for straight-thru traffic.

[talllguy]

We also have these in Maryland, like at MD-134 and MD-139 (Bellona @ Charles). Note that this signal has a protected right turn. MD-134 ends at this signal, and beyond it becomes Bellona Ave (unsigned CO1336). As I write this, I'm becoming a bit confused in the logic. Explain?

Note that most traffic here would be turning right, as there are better ways to get from the town along this route, to points north.

[vdeane]

In my city there are a few intersections, such as this one, where the road breaks into two lanes approaching the signal, and both continuing-straight and left-turning traffic are directed to use the left lane, while the right lane becomes right-turn only. I can't fathom why the lanes are configured this way, especially since there's no protected left turn, meaning that anyone who wants to keep going straight has to wait behind anyone who might want to turn left, which isn't easy to do because there's often a steady stream of traffic coming from the other direction. Heck, at certain times of day, it can sometimes only be possible for one car to make a left turn there during a green light, and only by waiting until the very end of the cycle. As it stands, people will often (technically illegally) use the right lane to go around left-turning vehicles anyway.

What am I missing? Is there a good traffic engineering reason why keeping-straight and right-turning traffic can't share the right lane?

Right on red.  Who wants to be stuck behind someone going straight?  Plus you can pass left turning traffic on the right.  Everyone does it.

[tradephoric]

We also have these in Maryland, like at MD-134 and MD-139 (Bellona @ Charles). Note that this signal has a protected right turn. MD-134 ends at this signal, and beyond it becomes Bellona Ave (unsigned CO1336). As I write this, I'm becoming a bit confused in the logic. Explain?

Note that most traffic here would be turning right, as there are better ways to get from the town along this route, to points north.

A general comment...there is no pavement markings indicating that the right lane is a dedicated right turn lane.  I can see how someone unfamiliar with the intersection would get into the right lane thinking it's a through lane.   Yes, there is a "right only" sign at the intersection itself, but by the time the driver sees that sign they are already in the wrong lane.

[getemngo]

We also have these in Maryland, like at MD-134 and MD-139 (Bellona @ Charles). Note that this signal has a protected right turn. MD-134 ends at this signal, and beyond it becomes Bellona Ave (unsigned CO1336). As I write this, I'm becoming a bit confused in the logic. Explain?

Note that most traffic here would be turning right, as there are better ways to get from the town along this route, to points north.

A general comment...there is no pavement markings indicating that the right lane is a dedicated right turn lane.  I can see how someone unfamiliar with the intersection would get into the right lane thinking it's a through lane.   Yes, there is a "right only" sign at the intersection itself, but by the time the driver sees that sign they are already in the wrong lane.

We could probably devote another topic to this, but a huge pet peeve of mine is intersections where there's nothing indicating which movements are permitted from which lanes (and it's not obvious). I've never seen this with more than 2 lanes in each direction, thankfully.

[wphiii]

Also in regards to the OP's GSV: Traffic going straight in the left lane continues straight.  Traffic in the right lane would have to swerve to get back to the left.  While this condition does exist at countless intersections throughout the country, it's not the optimal setup for straight-thru traffic.

It's funny that you should say that, because literally the next signal down the block from the one in the original post utilizes the left lane left-turn-only/right lane straight-and-right-turn setup I had been advocating. Granted, the parking lane on the other side doesn't begin for a couple hundred feet, unlike the previous intersection, but that's because there's a major bus stop there, so there are often buses pulled over to the right just on the other side of the signal. In my experience, this intersection tends to be much more free-flowing because of through traffic not getting backed up behind cars waiting to make a left turn. It still just seems odd to me that they'd use two different configurations for two pretty similar situations.

[talllguy]

We also have these in Maryland, like at MD-134 and MD-139 (Bellona @ Charles). Note that this signal has a protected right turn. MD-134 ends at this signal, and beyond it becomes Bellona Ave (unsigned CO1336). As I write this, I'm becoming a bit confused in the logic. Explain?

Note that most traffic here would be turning right, as there are better ways to get from the town along this route, to points north.

A general comment...there is no pavement markings indicating that the right lane is a dedicated right turn lane.  I can see how someone unfamiliar with the intersection would get into the right lane thinking it's a through lane.   Yes, there is a "right only" sign at the intersection itself, but by the time the driver sees that sign they are already in the wrong lane.

Good idea about the pavement marking. I'll send it up the chain and maybe SHA will do it.

[tdindy88]

We could probably devote another topic to this, but a huge pet peeve of mine is intersections where there's nothing indicating which movements are permitted from which lanes (and it's not obvious). I've never seen this with more than 2 lanes in each direction, thankfully.

I used to have to travel through an intersection like this when I went to school. Here's a map of the intersection.

https://www.google.com/maps/place/Indianapolis,+IN/@39.6721875,-86.1296327,85m/data=!3m1!1e3!4m2!3m1!1s0x886b50ffa7796a03:0xd68e9df640b9ea7c

Basically it depended on who was there and where they were turning and if they were turning. If the car in the left lane was turning left, through traffic (which was me all the time) proceeded to the right lane to go straight. If the car in the left lane was going straight, then the right lane became the right-turn lane, but there were no signs or markings to indicate officially which was which, you just had to go with the flow depending on the traffic. There were several more intersections like these I believe, maybe a lot more.

[mrsman]

If I'm at a street that is wide enough for two through lanes and two parking lanes and I'm coming up at a major intersection, I would think that the best way to handle it would be to not have any signs.  If nobody is turning, I'd stay in the left lane, becuase if I moved to the right, I'd just have to merge back in just after the intersection, since the right lane is blocked by parked cars.  But if there is a left turner in front of me, I'd like to pass him on the right, and I won't like having a sign that requires me to turn right if I'm in the right lane.

The right lane must turn right is only justified if it's a major movement and there is a separate right turn phase (contemparaneous with the corresponding left turn.)

[getemngo]

If I'm at a street that is wide enough for two through lanes and two parking lanes and I'm coming up at a major intersection, I would think that the best way to handle it would be to not have any signs.  If nobody is turning, I'd stay in the left lane, becuase if I moved to the right, I'd just have to merge back in just after the intersection, since the right lane is blocked by parked cars.  But if there is a left turner in front of me, I'd like to pass him on the right, and I won't like having a sign that requires me to turn right if I'm in the right lane.

The right lane must turn right is only justified if it's a major movement and there is a separate right turn phase (contemparaneous with the corresponding left turn.)

There's a problem with this that I encountered many times with an intersection in the area I grew up (until it got a dedicated left turn lane).

When the light is red, if the first car that arrives is turning left, no problem. All the cars turning left sit in the left lane, and all the thru/right traffic sits in the right lane. And if no traffic is turning left, the through cars take the left lane and right turning traffic takes the right lane. Again, no problem.

But if the first car or two at the red light is going straight (using the left lane), then a left turning car arrives behind them... all the traffic behind the left turning car moves into the right lane, assuming they're behind a line of cars that are all turning left. You have through traffic in both lanes, and once the signal turns green, they have to unexpectedly and awkwardly merge together on the far side of the intersection.

I've never seen any accidents happen this way, but this was a road with a paved shoulder beyond the intersection, and there were still a lot of close calls.

[jakeroot]

Right on red.  Who wants to be stuck behind someone going straight?  Plus you can pass left turning traffic on the right.  Everyone does it.

Yeah but...



Not saying it's the solve-all solution. But at least you don't have to worry about being stuck. I guess it's the guilt-approach to traffic engineering.

[agentsteel53]

Not saying it's the solve-all solution.

this would be the solve-all solution.

[vdeane]

Right on red.  Who wants to be stuck behind someone going straight?  Plus you can pass left turning traffic on the right.  Everyone does it.

Yeah but...



Not saying it's the solve-all solution. But at least you don't have to worry about being stuck. I guess it's the guilt-approach to traffic engineering.

No turn on red shouldn't even be allowed unless there's a major visibility obstruction preventing the maneuver from being safely done.

[TEG24601]

I have never understood the logic if this intersection arrangement.  It is counter intuitive to say the least, especially in states where you are prohibited from passing the driver turning left on the right, even if there is room (like Washington).  If you are allowed to pass on the right, this can make sense, as those locations where you can bypass the vehicle in the intersection this it isn't so daft.

[Brandon]

I have never understood the logic if this intersection arrangement.  It is counter intuitive to say the least, especially in states where you are prohibited from passing the driver turning left on the right, even if there is room (like Washington).  If you are allowed to pass on the right, this can make sense, as those locations where you can bypass the vehicle in the intersection this it isn't so daft.

The times I've seen this intersection arrangement is when the volume of right turning traffic is high when compared to that either turning left or going straight.  That's about, IMHO, the only real time it makes sense.

[vdeane]

I have never understood the logic if this intersection arrangement.  It is counter intuitive to say the least, especially in states where you are prohibited from passing the driver turning left on the right, even if there is room (like Washington).  If you are allowed to pass on the right, this can make sense, as those locations where you can bypass the vehicle in the intersection this it isn't so daft.

Whether it's illegal or not won't stop most people.  As far as I'm concerned, states where it's illegal should make it legal.  It makes live easier for everyone and harms no one.

[jeffandnicole]

I have never understood the logic if this intersection arrangement.  It is counter intuitive to say the least, especially in states where you are prohibited from passing the driver turning left on the right, even if there is room (like Washington).  If you are allowed to pass on the right, this can make sense, as those locations where you can bypass the vehicle in the intersection this it isn't so daft.

That's usually only in cases of a marked shoulder. At most intersections with traffic lights, there isn't a marked shoulder.

[jakeroot]

Right on red.  Who wants to be stuck behind someone going straight?  Plus you can pass left turning traffic on the right.  Everyone does it.

Yeah but...

[no right turn on red]

Not saying it's the solve-all solution. But at least you don't have to worry about being stuck. I guess it's the guilt-approach to traffic engineering.

No turn on red shouldn't even be allowed unless there's a major visibility obstruction preventing the maneuver from being safely done.

I visited the UK last week and not once was I angry that I couldn't turn left on red. Why? They've engineered everything else so properly that you don't really feel rushed. They set the stop lines back from the intersection like 10 feet for bike boxes, and they've installed thousands of roundabouts so when you do meet a signal that is red, you don't feel like your overall travel is being impeded. And apparently, it's a safer thing too; they have 3 fatalities per 100,000 people, whereas we have about 10 per 100,000. Right on red is just something that, while seemingly logical, just contributes to stress and anger. As an example, if right on red were illegal, your situation would not exist (being stuck behind someone going straight).

In theory, not allowing right on red (minus via slip lanes) could increase overall traffic flow, as traffic engineers wouldn't feel pressured to install dedicated right turn lanes, and as such, you could have more thru-lanes and/or no need to build wider roads to accommodate right-only lanes.

Does any of that make sense? Sorry, I am rather tired. Still stuck in Greenwich Mean Time.

[getemngo]

I have never understood the logic if this intersection arrangement.  It is counter intuitive to say the least, especially in states where you are prohibited from passing the driver turning left on the right, even if there is room (like Washington).  If you are allowed to pass on the right, this can make sense, as those locations where you can bypass the vehicle in the intersection this it isn't so daft.

Whether it's illegal or not won't stop most people.  As far as I'm concerned, states where it's illegal should make it legal.  It makes live easier for everyone and harms no one.

I wouldn't say it "harms no one". I've seen accidents occur from passing a left-turning car on the right. Two lane road, paved shoulder. Car is turning left. Everyone approaching from behind passes on the right, without giving any indication of what they're doing. Cars at the back of the line aren't expecting the obstruction, and have to swerve faster and faster to avoid the stopped car. Eventually, an elderly or inattentive driver rear-ends the car that's waiting to turn.

In one case, the car turning left already had its wheels pointing left and wound up getting hit by opposing traffic after being rear-ended. Killed a mother and kids. MDOT, of course, installed a dedicated left turn lane after the fact.

Granted, this was in a 55 zone, but there are places where passing a turning car on the right is acceptable and places where it isn't.

[agentsteel53]

I've seen accidents occur from passing a left-turning car on the right.

Eventually, an elderly or inattentive driver rear-ends the car that's waiting to turn.

seems to me the accidents occur from failing to pass a left-turning car on the right.

who wants to revisit mandatory re-licensing road tests every N years?  what, no elderly or inattentive senators?  okay, let's just give ourselves pay raises instead.