Defining the Problem

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Congestion on a highway can be caused by any number of factors, such as the weather, accidents, construction, heavy merges, and even narrowing lanes. 

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We can't do anything about the weather. If there is standing water or snow and ice on a highway, traffic should slow down.

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We also can't do anything about rubberneckers at an accident. There are people who will drive slowly, and even stop, to get a good look at an accident even if the lane in front of them is open. We wish we could cure the curiosity.

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Apart from one-time problems like weather or accidents, most congestion on a highway can be reduced by using specific traffic management techniques. Determining which technique to use requires identifying what is causing the congestion in the first place. 

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CMHO Consulting divides congestion on highways into two distinct classifications, clear-road congestion and congestion caused by bottlenecks.

 

Clear-road congestion is what happens when traffic slows down or stops on the highway, but there is no apparent reason. Traffic in all lanes can be driving the speed limit, then traffic in all lanes comes to a complete stop. After a period of time, anywhere from seconds to minutes, the traffic suddenly clears, and then the traffic is driving the speed limit again, with no apparent reason for the slow-down. The road is clear of any identifiable problem, such accidents, debris, or weather, and yet there is congestion.  

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Bottlenecks differ from clear-road congestion in that there is a specific cause for the congestion. Bottlenecks can occur where there are heavy merges, they can occur where there are lane drops, such as when four lanes merge into three, they can occur where there is construction, and they can even occur where lanes suddenly become narrower.

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Identifying the Problem

 

When traffic is backed up for fifteen miles on a highway, driving stop-and-go, bumper-to-bumper, it can sometimes be difficult to determine what caused the problem in the first place. 

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A popular "explanation" for congestion is that there are too-many-cars trying to use not-enough-highway. However, "Too many cars on the road" is not an excuse for stop-and-go traffic. Almost all recurring stop-and-go traffic can be eliminated in a matter of a few weeks.

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In the absence of one-time problems, the most likely reason for a car to stop on a highway is because the car in front of it is stopped. Before you suggest how obvious that is, consider this: What exactly made the first car stop? The only way to fix the problem is to figure out why the first car stopped. 

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When CMHO Consulting starts a program to reduce congestion on a highway, we know that we have to identify where the congestion begins and why it begins. With our experience, we know what to look for, but that doesn't mean that it happens immediately. 

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If there is an obvious bottleneck, it is reasonably easy to understand the dynamics that cause traffic to stop. It is less clear why cars stop when there does not appear to be a bottleneck. However, if the traffic backs up in the same place every day, there has to be a reason.

 

If there is a specific location on a highway where congestion occurs on a regular basis, but there is no obvious bottleneck, we start by spending some time studying the highway so that we can observe the problem as it begins in order to understand what causes it. We have to determine why the congestion begins in order to fix it.

 

As opposed to bottlenecks, which occur in the same place every day, clear-road congestion can happen anywhere. The problem with clear-road congestion is that it can back up traffic for miles, with no apparent cause, and it may not happen in the same place two days in a row. If there is only intermittent congestion at a specific location, it has to be clear-road congestion.

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Fixing the Problem

 

Unless CMHO Consulting is asked to address a bottleneck specifically (see below), our strategy is to begin to reduce congestion immediately. The first step to reduce congestion on any highway is to implement a traffic management program to reduce clear-road congestion.

 

Clear-road congestion can be reduced easily, quickly, and at very little cost. Since only the state DOT has the authority to implement any traffic management programs, CMHO Consulting will explain how the program works to the DOT. We will show the DOT how to initiate the program, and we will show the DOT how to explain the program to the public.

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For any highway with three or more lanes in each direction, if there is no bottleneck, and in the absence of any one-time issues, such as accidents or weather, it is the position of CMHO Consulting that the left lane should never have any stop-and-go traffic. 

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It is logical to expect that the right lanes of a highway will have the most congestion because of traffic entering and exiting the highway. However, whenever a back-up begins, it is usually the left lanes that back up first and farthest. 

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In the picture below, the right lane in each direction has fairly light traffic, but the left lane in each direction is either stopped or almost stopped. It is this kind of clear-road congestion in the left lanes that we target first.

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The hallmark of our strategy is to achieve a dramatic increase in the speed of traffic in the left lanes of a highway in a short period of time. The easiest congestion to fix on any highway is stop-and-go traffic in the left lanes. 

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Depending on the scope of the initial implementation, it may take the DOT a few days to set up the program, but once the program is initiated, there are clear expectations:

 

• There should be an obvious reduction in congestion in a matter of days.

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• For any highway with three or more lanes in each direction, there should be an obvious reduction in stop-and-go traffic in the left lane in a matter of days.

 

• For any highway with three or more lanes in each direction, there should be an obvious increase in travel speed in the left lane in a matter of days.

 

• For any highway with three or more lanes in each direction, within four weeks, the stop-and-go traffic in the left lane should be essentially eliminated.​

 

By reducing the congestion in the left lanes, we increase the throughput of the left lanes, which can reduce the amount of congestion in all lanes.

 

For example, consider a highway with four lanes in each direction which has a 60 mph speed limit and average rush-hour speeds of 15 mph. If we increase the average speed in the two left lanes to 30 mph by eliminating stop-and-go conditions, we cut the commute time in half, and we double the throughput of the left lanes. That's like building two new extra lanes.

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If we increase the average speed in the two left lanes to 45 mph, we cut the commute time by two-thirds, and we increase the throughput by 200%. That's like building four extra lanes, but commuters don't have to suffer through delays due to construction, and taxpayers save $100's of millions in construction cost.

 

When the left lanes start moving faster, some drivers in the right lanes will move left, thereby reducing congestion in the right lanes as well.

 

Once the congestion in the left lanes is reduced, it becomes much easier to determine what is causing congestion in the right lanes.

 

Usually, traffic enters and exits the highway using the right lane. Vehicles trying to merge onto the highway and vehicles trying to get off the highway can both slow down traffic on the highway in the right lane and often in the lane next to it as well.

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The picture below shows typical congestion. Traffic is stop-and-go across all three lanes, traffic on the on-ramp is stopped and backed up, and there is a white SUV trying to merge into the right lane right before the on-ramp. This highway is a mess. Now, the question is whether the traffic entering the highway is causing the stop-and-go traffic across all three lanes, which would suggest that the congestion can be relieved by improving the on-ramp. The only way to determine the answer is to eliminate the stop-and-go traffic in the left lane.

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CMHO Consulting offers a traffic management program for improving the flow of traffic in the right lanes of a highway as well, making it easier for vehicles to get off the highway and also making it easier for vehicles to merge onto the highway without slowing traffic down. There should never be traffic congestion in the right lanes like the congestion in the picture.

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Fixing Bottlenecks

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Our program to eliminate clear-road congestion is the fastest and easiest way to achieve a significant improvement in the flow of traffic over a short period of time. Once the clear-road program has been implemented, we start working on bottlenecks.

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Bottlenecks have to be addressed on a case-by-case basis. A lane-drop merge is not the same as a heavy merge where traffic from one highway enters another one. Regardless of the type of bottleneck, congestion at all bottlenecks can be reduced to some degree quickly and easily using traffic management programs. 

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Some bottlenecks are caused by inferior roadway design. It is sometimes difficult to use traffic management to resolve design problems that force congestion to occur. In such cases, CMHO Consulting recommends ways to improve the situation by adding or moving barricades or by changing roadway striping. Congestion at most bottlenecks can be reduced without the need for any new construction.

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The congestion at most bottlenecks can be reduced quickly, easily, and at very low cost, but each bottleneck must be addressed separately. If each bottleneck can be resolved in a matter of two to three weeks, but there are several bottlenecks along a highway, improving the whole highway can take up to several months. 

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