Unlocking secrets of gridlock

by Julia Kuzeljevich

It’s a monster that feeds on miles of metal, glass, and rubber, and it seems to grow larger with every passing day.

With an increase in traffic volume comes congestion. With volume and congestion comes frustration, and an increasing frequency of accidents that can essentially shut down highways for hours on end.

Call it what you will, but there is a science to the crush of traffic that is making a mockery of the spirit of the open road that’s sold in the lyrics of country music songs.

“There are three elements to congestion. We talk about recurring congestion, which is normal peak demand being heavier than supply, and we talk about non-recurring congestion, such as a parade, or a collision,” says Les Kelman, Toronto’s director of transportation systems.

The third kind of congestion, says Kelman, would be more applicable to an urban area. “It’s the illegal maneuver congestion, such as illegal turns and parking,” he says. That means other vehicles have to manipulate around obstacles that shouldn’t be there, such as impatient road hogs.

In terms of mathematics, those who study the crush of traffic relate it to the number of vehicles passing through during a regular time interval.

“If there are irregularities in the system, traffic congestion will occur from time to time. But on average, a vehicle can merge into traffic smoothly at 30-second intervals,” says Professor Sudha Jain of the statistics department at the University of Toronto.

The rate of arrival, or rate at which vehicles start moving onto a ramp or collector lane to merge into traffic, has a lot to do with whether congestion can be expected.

If there is sufficient volume, says Jain, a large queue develops. “Or the rate of arrival may be so low that, for a couple of kilometres, the highway is empty, but then another few kilometres down there is a rush,” she says. Depending on where the traffic enters the highway system, that particular collector lane (known as an acceleration lane when the car is coming onto the highway, or deceleration lane when it is exiting) may be particularly well traveled, because it feeds into another highway system or from a very busy intersection.

Where no cars are merging into the flow of traffic from a collector, the route may look like clear sailing ahead, until you see the brake lights of the stropped vehicle you are fast approaching.

“There are many mathematical and statistical models on traffic flow, but they can help only in the prediction. When we measure congestion mathematically, we must know the average time value for the vehicle to merge, the average time that the highway is empty, and the (probable) distribution of cars on the road. Then, theoretically, we can predict congestion, and perhaps suggest some modifications,” says Jain.

And there are new approaches to managing the crush of traffic.

Some advanced traffic management specialists speak of metering (already in place on southern Ontario’s Queen Elizabeth Way and in numerous U.S. freeway systems) as a way to keep sufficient space between merging vehicles. Essentially, it’s a traffic light system for on-ramps.

“It’s partly used for rush hour so you don’t have a pack of cars bumper-to-bumper. You’re only stopped for, say, five or six seconds but it helps improve the merging. Some people don’t like it, but it helps keep the main line moving,” says Will MacKenzie of Ontario’s Ministry of Transportation.

When there is more volume on the road, resulting in wear and tear, how can construction projects be accomplished without adding to the problem?

” Most of our construction work is done late at night, from 11 p.m. to 5 a.m., when volumes are at their lowest,” says MacKenzie.

But as anyone who drives the nation’s highways knows, one little blockage is all it takes to cause a sufficient backup.

“It basically works out to this: if there is a lane closure or blockage that reduces the available choice of lanes, one minute of closure works out to roughly 10 minutes of congestion,” says MacKenzie. “If a lane were closed for 20 minutes, it would take an hour or two to clear, depending on the time of day,” he says.

At peak periods, any kind of delay, such as a stalled car that hasn’t been pulled out of the lane, means that you are essentially sentenced to slow down, and perhaps change your route.

“Nowadays, you see greater emphasis on traffic management over suggestions to create more infrastructure. It’s a less-expensive means of making greater use of existing infrastructure. The COMPASS system, (an electronic sensor system that measures how fast vehicles are traveling, and then posts the information on electronic signs) is helping us to respond more quickly,” says MacKenzie. Because the electronic signs are close to transfer lanes, motorists are offered advanced warning of a blockage so they can try to detour or leave.

Although the COMPASS system does not do an actual count of the number of vehicles passing over the sensors, it does measure speed. When the electronic signs read “Moving well”, speeds are clocking in at 75-80 km-h. From 40-70 km-h, the highway is “moving slowly”, and below 40 km-h, “verrrrrrry slowly.”

The system updates automatically every 60 seconds. “If, however, all the lanes are blocked and nothing’s moving, we manually input the signs’ information,” he says.

Sometimes, that’s about all they can do. When it comes to accidents, they’re the jurisdiction of the police.

“The police take charge of the scene at a total road closure, to do a thorough investigation, although we are often there carrying out the closure at their direction,” says MacKenzie.

In order to examine some of the delays that accidents can cause, an Ontario Red Tape Review Commission has been set up to investigate accident clean-ups and highway re-openings. The Ontario Trucking Association’s manager of safety and operations, Barrie Montague, will participate in the review group.

“Our concern, in an accident involving a commercial vehicle, has been to protect the carrier from further losses by some inappropriate losses at the scene. This is particularly relevant when it’s not his fault,” says Montague.

Such damage could be caused, say, when a bulldozer is used to clear wreckage off to the side of the highway. This approach, used on some toll routes recently, caught the attention of Ontario officials, although they later seemed to cool to the idea.

“The review process is ongoing. We’ll be looking at what the options could be in terms of trying to reduce the time it takes to re-open highways. But the Ministry’s priority is road safety,” says Bob Nichols of the Ontario Ministry of Transportation.

Safety is paramount, especially on stretches of highway in heavily populated urban areas, or on routes close to border crossings with the U.S., where there is less and less room to extend the number of lanes on highways.

“If you increase the number of lanes, you increase the supply. You don’t necessarily decrease the demand,” says Jain. Sometimes a major congestion problem has a very localized solution. It could be one on-ramp, for example, that causes a dreaded bottleneck.

“Recurring congestion is really a question of demand management,” says Kelman. “High-occupancy vehicle lanes, such as for buses or carpools, are a solution for urban congestion. As cities move into the high end of demand management, they may even look at charging for high-peak travel.”

Some motorists around Toronto have already shown their willingness to pay, driving the tolled Hwy. 407 that stretches across the top of the city.

“There’s no room for traffic expansion along many of the highways in urban areas, except at exorbitant cost. The 407 (the toll highway built above the city of Toronto) has eased that congestion, although many truckers may be reluctant to use it. But without the 407, the 401 would be really bad. And in British Columbia, the fastest route from coast to interior, the Coquihalla, is a toll road,” says MacKenzie.

While levels of congestion are obviously important in planning future roadwork, they aren’t the only factor to be considered.

s aren’t built for rush hour, but for average daily traffic. Otherwise, they’d be 75 lanes wide. There are a number of areas where we are extending acceleration or deceleration lanes. Sometimes just extending them helps to merge the flow. We’re always fine-tuning as much as we can,” says MacKenzie.

Besides pouring money into highway upkeep, some say there are other ways to combat increased congestion and the resulting social stress, like road rage.

“Every modification has a cost. We could look into regularizing arrival times on the highways systems by encouraging flexible working hours,” says Jain. “Then we could perhaps space out the volume of traffic more equally.”

Jain is also a proponent of having a priority lane, or even a separate ramp, for trucks.

“Sometimes I find that ramps are single-lane, and trucks are heavy, and have to slow down to travel the ramps, which slows everything else down,” she says.

Maybe unbearable congestion will become a sign that a healthy economy can often be too much of a good thing.

“The way manufacturing is going, the potential economic damage for shutdown is more severe, especially given just-in-time delivery. And the transportation network is like the arteries of the body – it has to be kept active and healthy,” says Kelman. n

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