Lane discipline, speed differentials, and heavy traffic

[briantroutman]

Very long, slow drives on both I-5 and CA 99 going between SF and LA this weekend got me thinking about what should happen to the concept of lane discipline in high-traffic situations.

In the example I'm thinking of, we have a four-lane freeway with a speed limit of 70 for cars and 55 for trucks. The speed limit is a bit of a red herring, though—the speed differential could be caused by driver preference, the inability to go faster due to a grade, etc. The left lane is bumper-to-bumper with cars going an average of about 62; the right lane is very sparsely filled—heavy trucks and slower cars averaging a little over 50. And from a driver's vantage point, the left lane is jammed this way as far as can be seen.

(Click image to view full size.)


The X column gives you a zoomed-out view of the scenario.

Column 1 shows you the situation with which we're probably all familiar. You may have come upon the situation quickly, not realizing that traffic was stacking up because of an impediment in the right lane. But if you're one of the motorists in the right lane, all you can do is keep your left turn signal flashing and hope someone lets you in—or just force your way in and hope a collision doesn't result.

Let's say that you're driving the dark blue car in Column 2. You've been maintaining the average left lane speed and just passed a slow-moving truck, but you see that the backlog continues ahead with another slow-moving truck in the right lane less than 500 feet ahead. What is your obligation to move back into the right lane? And what if your speed (and the prevailing speed in the left lane) isn't 62-63 but rather 70, 75, or higher? Would that change what you should do?

If you're willing to be assertive (or, depending on your point of view, if you're willing to be a dick), you can make modest gains in queue position by cutting into the right lane as soon as you pass a truck (as in Column 3), flooring it until you reach the next truck, then cutting back into the left lane.

Clearly, something's not working properly when half of the lane mileage for a stretch of highway is nearly vacant, reserved for the slowest 5% of vehicles on the road. And while I live by "KEEP RIGHT - PASS LEFT" (and curse those who don't), I can understand the hesitancy of motorists to use the right lane when doing so in this kind of extremely heavy traffic may mean spending several frustrating minutes riding the back bumper of a big rig while trying to get back into the left lane.

How do you handle situations like this? What do you think is the right thing to do? And adding lane capacity, what do you think is the best public policy for managing these situations?

[Alps]

New Jersey is a #3 state. Traffic fills every available gap out of necessity, so when you have slow-moving vehicles spaced apart, someone will find a way to gain a spot, or at least try. If I'm not a #3 vehicle (and I wouldn't be at 84 in a 70, mind you), then I am one of the left lane vehicles who moves up within a few feet of the next car to avoid being cut off by a #3 vehicle.

[wxfree]

My tendency is to get back in the right lane as much as possible, unless traffic is so heavy that I might get stuck behind a slow truck.  When I get in the right lane, the cars behind me often move quickly to the next blockage ahead and slow back down, an inefficient maneuver.  Still, I'd rather have drivers in a hurry in front of me than behind.

In situation 2 I'd move to the right lane and later get back in the left.  In the other situations I'd stay in the left lane since me moving right wouldn't benefit anyone.  If I did get stuck behind a truck, I'd appreciate the 56 mph I had and not despair the 6 mph I was losing.  In no case would I risk a collision to prevent some male urinary meatus from feeling like he'd cheated the system by risking his life to gain 5 seconds.

I'm usually in the right lane going the speed limit, or whatever speed keeps up in that lane.  Sometimes I see the left lane much more filled while the right lane(s) is (are) half empty.  If two or three right lanes are moving at about the same speed and all half-empty, while the left lane is full of cars going faster, then it would seem that capacity is being wasted. I haven't paid enough attention to know how common that is.

[Duke87]

While I have no problem passing slow people on the right, I always look ahead in both lanes before I attempt to do so. If I do not have both clear space in the right lane and a gap in the left lane ahead to slip back into, I'll just stay where I am... because I know from experience that attempting otherwise will end up with me either right back where I started or allowing more cars to pass me before I can move back left (i.e. worse than if I had just stayed put).

At the same time, I have no problem moving right if someone behind me seems to want to go faster than me. I hate it when people are obstacles to me, and I try to avoid being an obstacle to others.


What I might propose as a bit of driver discipline in the simple scenario proposed: the rear truck in the right lane should try and maintain a safe following distance but nothing much beyond that. This situation could be made less problematic if those two trucks were closer together and thus all the cars could get around them faster.

Of course, if truck traffic is high enough that there are more trucks spaced out like that for an extended distance, then that doesn't help much.

[jeffandnicole]

While I have no problem passing slow people on the right, I always look ahead in both lanes before I attempt to do so. If I do not have both clear space in the right lane and a gap in the left lane ahead to slip back into, I'll just stay where I am... because I know from experience that attempting otherwise will end up with me either right back where I started or allowing more cars to pass me before I can move back left (i.e. worse than if I had just stayed put).

At the same time, I have no problem moving right if someone behind me seems to want to go faster than me. I hate it when people are obstacles to me, and I try to avoid being an obstacle to others.


What I might propose as a bit of driver discipline in the simple scenario proposed: the rear truck in the right lane should try and maintain a safe following distance but nothing much beyond that. This situation could be made less problematic if those two trucks were closer together and thus all the cars could get around them faster.

Of course, if truck traffic is high enough that there are more trucks spaced out like that for an extended distance, then that doesn't help much.

There's a big difference between safe following distance and being close together.  Safe distance, for trucks, at 60 mph or so, is several hundred feet - plenty of room for cars to jump in and get around other traffic.  If the trucks were closer together, it would reduce (but not prevent) cars from trying to get in and pass others, but then the trucks wouldn't be maintaining a safe distance.

[Occidental Tourist]

The number 3 illustration is the standard LA to Vegas drive between Barstow and the state line.

[agentsteel53]

scenario 2: blue car is accelerating away from truck.  in about 1-2 seconds he will move over to the right.

oh wait, this is America.  oopsie.

[Brandon]

scenario 2: blue car is accelerating away from truck.  in about 1-2 seconds he will move over to the right.

oh wait, this is America.  oopsie.

  Thanks for the laugh.  In Illinois, the asshole would just sit there while a few try passing him on the right, and a few more would get burned and then try to bull their way back into the conga line.

[Indyroads]

This scenario plays itself out in every state on all 4 lane freeways. This is largely due to lack of courtesy and observation of slower traffic keep right rules that apply to the freeways. Not all states have Keep Right rules but it is largely accepted as a general rule of the road. The only real way to effectively deal with rolling roadblocks like these is to widen freeway capacity on these congested highways to 6 lanes.

[roadman65]

At least somebody other than me noticed that one.  You cannot leave the proper one car length for every 10 mph of speed traveling as another motorist will come out of someplace and fill in the gap. 

Lately I have been noticing that many cars will not just fill the gap, but use the gap to make a right turn (or even a left turn) as they will be two lanes over and want to make a turn at an intersection, so they cut across the lane in between like it was nothing and make the turn instead of planning ahead and moving to the proper lane before hand.  What is even scary about it is, that I think most of these drivers actually forgot about the turn that they're supposed to make and are doing a quick fix.  That means that there are too many careless people in this world, as mistakes like this should be one in a million, but are one in every five.

[jakeroot]

This scenario plays itself out in every state on all 4 lane freeways

Indeed, but even with more than 4 lanes it seems to happen, at least here in Seattle. Near SeaTac (the airport area), the 5 is 12 lanes, and yet, I still find myself in a line of cars in the far left (non-HOV) lanes. The trucks (particularly those from BC) tend to stay in the left 2-3 lanes because a) those lanes are the ones they arrived in from either north or south of the metro, and they didn't bother to change lanes, or b) they are passing slower moving trucks which are in the farther right lanes at a VERY slow rate, forcing every single car into the left 2 lanes if they even want to consider overtaking. Of course, the other lanes are usually being held up by Subaru Outbacks (not a stereotype, actual fact).



ALSO: this is my first diagram. Sorry it sucks so much.

[TEG24601]

That seems about right Jake.


I'm still unsure about the logic of the trucks running at a different speed that autos.  If it was a safety concern, they would legislate better safety equipment (brakes, etc) for the trucks.  My father is convinced it is simply to slow the traffic because the legislators don't think people actually need to go the speed limit.  However, I can say for certain that I am a much happier driver when the trucks have the ability to travel at high speeds.


The first thing I would to to solve the situation is to remove the differential, even if that means finding a mean speed for everyone.  If that does not solve the issue, then I would add capacity.

[Davidwrangley]

well Jake,  you displayed good map about road discipline. I appreciate your work and also speed limit. As we all know that speed limit help to reduce road accident that secure the life.