How we are harassed by cars, causing traffic jams and collapses

2024 Author: Seth Attwood | [email protected]. Last modified: 2023-12-16 15:55

The construction of highways worsens the situation on the roads. New routes lead to traffic collapse. Navigators accelerate congestion. Why seemingly the right measures exacerbate the problem with traffic jams?

The authorities cheerfully report on what has been done to improve the situation on the roads, and moving around the city takes more and more time. Motorists consider traffic jams to be the result of a corrupt conspiracy or the total incompetence of officials, because everyone who has a car is sure that he knows the answers to eternal Russian questions.

WHO'S GUILTY?

ROADS

A fundamental characteristic of a road that determines whether traffic jams will occur on it is throughput. And its limit is about 1,500 cars per hour per strip. Neither the quality of the asphalt, nor the bumpers, nor the markings are able to increase this indicator, because the cars must keep a distance of several seconds and they have a physical size. “Moreover, the throughput of a road is generally determined by the throughput of its narrowest point,” notes mathematician, senior lecturer at the Department of Complex Systems Modeling Technologies at the Higher School of Economics Yuri Dorn. - Let's say, if a beautiful five-lane highway 1000 km long in one place narrows to two lanes, its total capacity will be like a two-lane road. And even worse: due to the fact that the cars are slowing down, changing from five rows to two, the final throughput will be lower."

Roads have other features that seem to contradict common sense. So, with an increase in the speed of movement, the capacity of the road may decrease. “The number of cars passing through the cross-section of the street per unit of time, the speed of cars and traffic density in transport mechanics are connected by a simple formula N = vq,” explains Evgeny Nurminsky, an expert in mathematical modeling of traffic flows, professor of the Department of Mathematical Methods in Economics at the School of Natural Sciences of the Far Eastern Federal University. … - N is the traffic intensity, auto / h; v - vehicle speed, km / h; q - flow density, auto / km. By changing one parameter, we pull the rest along with us. If cars move at a speed of 200 km / h, traffic density will be very low, because drivers will have to maintain a long distance. Accordingly, the flow of cars, which is equal to the product of density and speed, will be less than it would be at a speed of 60 km / h."

THE CORK YOURSELF

While an increase in speed can lead to a decrease in traffic on the road, the same effect is achieved by a decrease in speed. Car traffic drops dramatically when cars go slower than 20 km / h. “At such a low speed, the maximum possible 1,500 cars per hour will not get out of the jam: they are moving too slowly for that. If only 1000 cars leave, 500 cars will be assembled in a traffic jam in an hour. Taking into account the physical size of the car (about five meters) and the distance to neighboring cars, a traffic jam is 2.5 km long, "a leading analyst of Yandex. Traffic jams "Leonid Mednikov. And new cars constantly drive up to the place of the congestion, so it may not dissolve for a very long time.

TECHNICS

What Yandex. Traffic jams"

The most popular service in Russia that displays congestion in real time is Yandex. Traffic jams". The drivers accuse him of "twisting" the data and misrepresenting the situation. Leading analyst of the service Leonid Mednikov answered the main complaints of users.

The workload of the city is determined based on the assessment of the situation on the main streets and highways, the list of which changes little. These roads form a "transport frame" that allows you to travel throughout the city. The service maintains a rating scale so that 10 points reflect truly "dead" traffic. If the ratings remain unchanged, then with a general deterioration of the situation in the city (alas!), The service will always give 10 points and drivers will not be able to adequately predict how long the trip will take.

Previously, roads with a speed higher than 30 km / h were shown in green, less than 15 km / h in red, everything in the middle was shown in yellow. But now the service uses a relative color gradation: it reflects the traffic congestion not in general, but in comparison with the usual situation for this place. Therefore, traffic on the “yellow” section of the Moscow Ring Road may in fact be faster than on the “green” section of a side street with traffic lights and crossings.

The service shows the predicted situation based on past data on a specific site. But the route is still being built without taking into account this information. Therefore, having left just before the evening rush hour, in the middle of the way you can get into a dense traffic jam, which formed in a few minutes. “Taking into account the forecast of the development of the situation is so far the only thing in which people are ahead of the navigator,” says Leonid Mednikov.

STRUCTURE OF THE CITY

One of the most efficient structures of the city, which allows the best distribution of traffic flows, is the square-nesting structure. But most cities in Russia have a ring structure with radius roads. Such cities were formed on the site of fortresses, gradually expanding. Such a structure was ideal for protection from belligerent neighbors, but traffic flows in ring cities are distributed as badly as possible: both the central ring highways and the exit highways, along which people get to the center in the morning and leave it in the evening, turn out to be overloaded. “In addition, in megalopolises with a ring structure, drivers experience colossal overruns, sometimes tens of kilometers per trip,” adds Yuri Dorn.

Scientists say that ring-shaped cities often have low connectivity. That is, there are few ways to get from one place to another, and cars accumulate on key roads that cannot pass otherwise.

Trying to unload the ever-standing highways connecting different districts of the city, the authorities are expanding the roads, but this is not effective. For example, many of Moscow's outbound highways run into a congested center at one end, and at the other end into densely populated sleeping bags. “Exit / entrance to such highways creates traffic congestion points, which, with the growth of the city, find themselves deep inside.

In addition, such highways cut the existing transport routes, Nurminsky notes. "To neutralize the harmful effect, you need to build many interchanges and detours, which refutes the original idea and is very costly."

PAYMENT

Vision angle

Traffic flows can be described with varying degrees of "approximation", and for this, a mathematical apparatus from different fields of science is used. Local decisions of drivers are modeled using the theory of cellular automata. To describe the behavior of traffic flows at the level of individual roads, the apparatus of hydrodynamics is used - the science of the behavior of fluids. Game theory and optimization theory are used to predict the load on the transport network and the distribution of flows along routes.

DRIVERS

Anyone who drives a car knows that a nanosecond is the time after which the driver from behind starts honking after turning on the green traffic light. Motorists who consider themselves reasonable are very annoyed at such moments, believing that a short delay will not affect the traffic situation. And they are wrong.“Driving slowness can provoke congestion,” Nurminsky says. - Traffic jam is a non-linear system with strong positive feedback, that is, in response to incoming signals, it behaves completely differently from what you expect. For example, you were on the phone while driving and slowed down. It seems to be okay, but all the drivers behind you are forced to slow down - and there is a traffic jam that can dissolve for an hour."

But the main reason for the increase in traffic jams is precisely the increased rationality of drivers. Even if for simplicity the motorist has a choice of two roads - of course, he will lean towards the fastest route. Other drivers who intend to drive in the same direction will do the same. As a result, a faster road is more likely to fill up with cars, its capacity is no longer enough - and a traffic jam forms. Motorists who left later, seeing that there was a traffic jam on their favorite route, take a longer, but easier road, because now the travel times on both routes are equal. If some of the drivers initially preferred a longer route, there would be no traffic jam on the short route.

The situation when the travel time on all actually used routes becomes the same is called the Nash - Wardrop equilibrium in transport modeling. In this state, no attempt by the driver to change the route can reduce the travel time. Moreover, as recently shown by scientists from Korea and the United States, throwing motorists on bypass roads in order to save a few minutes noticeably worsen the overall situation. When there are a lot of cars, the road situation inevitably comes to a Nash-Wardrop equilibrium. With the proliferation of navigators that show traffic jams, the “creep” into it has accelerated: drivers leaving later now immediately take a detour. But, as Yuri Dorn explains, navigators do not worsen the situation. They speed up the formation of traffic jams, but there are fewer cars in each - after all, some of the drivers immediately go along an alternative route. In addition, some motorists shift departure times to smooth out peak loads. Finally, thanks to navigators, many people learn about bypass roads. “Of course, for those drivers who previously rode freely on tricky routes, the situation became worse, but the total travel time on all roads fell. However, the total and even individual travel times can often increase,”Dorn concludes.

MOSCOW

In Russia, there are traffic jams in any large city, but the capital suffers most of all from them. “A huge number of activities are concentrated in Moscow, including quite specific ones: the financial sector, science and business. A person who works, say, in some institute, must go there. And for a salesperson or a person with another non-specialized profession, the link to a place is not so relevant,”says Dorn. In addition, the overwhelming share of jobs is concentrated in the center, while people live closer to the outskirts. As a result, pendulum flows are formed, occupying the same roads, on which there are traffic jams most of the day.

The high cost of housing in the center and the Russian habit of considering their own apartment a great value prevent people from moving closer to work. The idea of the capital's authorities to "relocate" officials to the outskirts has also quietly faded away. However, the transfer will not solve the problem: if the office where the official works is transferred from the center, say, to Mitino, but the official lives in Chertanovo, he will still go to work through half of Moscow.

WHAT TO DO?

DO NOT ATTEMPT TO REMOVE SEPARATE PLUGS

The main postulate of transport science is the same as in medicine: traffic jams must be dealt with before they appear. Actions that prevent congestions from forming will be fruitful, rather than attempts to eliminate the most harmful traffic jams on a point-by-point basis.“It is possible to correct the situation at locally ineffective places, sometimes it is enough to take some simple measures - for example, remove the left turn and make a U-turn 500 meters after the intersection. The traffic jam will go away from here, but it will not disappear at all, but simply move to another place,”explains Nurminsky.

MATHEMATICS

PARADOX OF BRESA

Construction of a new road linking existing ones could worsen the situation in the entire transport network. Since the roads are interconnected, the appearance of another section of the track, on which there are now always cars, increases the travel time on all routes. The situation can be improved by closing this "Braesov road". However, it is impossible to detect it: traffic jams do not accumulate on it, but on other routes.

POSTULATE LEWIS-MOHRIDGE

The more roads are built, the more cars appear. Some people prefer to change from public transport to personal.

DOWNS-THOMSON PARADOX

The average speed of a private vehicle depends on the speed at which public users get to their destination. The less developed public transport is, the more people prefer a private car.

PARADOX OF PIGU-NIGHT-DOWNS

Adding alternative roads, where people choose the route rationally (“selfishly”), leads to a stable balance: everyone drives their own vehicles, and the buses remain empty. Moreover, the travel time is the same.

DO NOT BUILD ROADS AND DO NOT INTRODUCE NEW ROUTES

The seemingly obvious decision to build as many roads as possible in order to increase the capacity of the transport network does not work either. “Seeing that there are a lot of free roads, a few million more people will switch to cars, and all new routes will also stop,” says Dorn. If the growing demand for roads is endlessly satisfied, sooner or later all the free space in the city will be built up with highways, where cars are parked around the clock.

Introducing new public transport routes haphazardly is also useless. “A typical example is the introduction of new subway stations on the outskirts,” says Dorn. “Considering that the capacity of key junctions in the center and the number of trains that can be run on one line are limited, such measures simply lead to“throwing”traffic jams in the metro."

INSERT THE LIGHTS

The traffic-free highways, loved by many motorists, are also exacerbating the traffic collapse. “Traffic lights thin out the flow and do not allow it to thicken,” explains Nurminsky. - Ideally, the task of a traffic light is to maintain an optimal traffic density at which the traffic flow is maximum. In the city, this is achieved at a speed of about 60 km / h."

MAKE PAID ROADS

In conditions that are typical for most large cities, when there are more people who want to travel on the roads than they can accommodate, routing becomes the most effective measure, that is, artificially reducing the attractiveness of certain paths. For example, by introducing a fare. “When the bandwidth limit is exceeded, you will definitely be wasting some resource to make up for the difference between the more and less efficient route. Usually these resources are time and nerves lost in traffic. Toll roads allow those who wish to compensate for this difference not with time, but with money,”explains Yuri Dorn.

Biting prices force people to change their habits: for example, to look for a job that allows them to partially work at home or postpone the time of departure. “Of course, people are less comfortable than they would be with empty roads. But there are no empty roads in cities for a long time: you need to compare the current situation with the situation when the city is in a traffic jam. For those who took a detour or left later, nothing has changed: the costs remain the same. But for those who decided to pay, the situation has improved. At the same time, the efficiency of the roads in general increases, since it is not measured by the absence of traffic jams, but by the total time that all travelers spent on the road,”notes Dorn.

LEARN ON SCIENCE

“The problems of road congestion can only be solved in a comprehensive manner, by calculating the long-term effects of all introduced measures using complex mathematical models,” says Yevgeny Nurminsky. "Science is a thoughtful lady, to give the correct answer, it needs time, and officials want everything to be done yesterday." Because of this, colossal money is often spent on projects that give zero effect or even worsen the situation on the roads.

The problem is further complicated by the fact that Russia is sorely lacking data on the basis of which it is possible to create adequate transport models. “In the United States, for example, this problem was solved by law: if a developer wants to receive subsidies for the construction of roads or buildings, he must submit a feasibility study, in which, according to certain methods, all construction parameters will be calculated. As a result, a lot of transport and analytical departments have appeared at the municipal levels, which prepare all the necessary information. This created a powerful order for transport specialists, and now almost every major American university has a transport research division,”says Nurminsky.

MECHANISM

Everything is logical

It often seems like the plug has formed for no reason. But there is an explanation for the mysterious congestion.

CORK OUT OF NOTHING

As a rule, an accident occurred on this section of the way, which was taken away long ago. While the cars were in place, the capacity of the road dropped from, say, 1,500 to 1,000 vehicles per hour. After the perpetrators of the accident leave the scene, the traffic jam remains until all the accumulated cars have passed. If 500 cars have gathered in an hour, then they will leave the traffic jam "for no reason" for another 20 minutes, and all this time new cars will get up at the tail of the traffic jam.

CONFLICTS IN BAD WEATHER

Even in the absence of accidents, road congestion rises: drivers tend to keep a safe distance, vehicle density and road capacity are falling.

Jammers on the other side of an accident

Such congestions are formed due to the curiosity of motorists. Even if the driver brakes slightly, all cars driving behind him are also forced to slow down. The capacity drops and this deceleration wave propagates downstream. Cars changing from one row to another give the same effect: they force several lanes to slow down at once.

CHANGE THINKING

It is impossible to destroy traffic jams in Russian cities without changing social stereotypes. “Solving the problem of how people get to the center and back every day is futile. You need to motivate people to choose other places to go,”says Dorn. But while jobs, especially in Moscow, are concentrated in the center, where housing is monstrously expensive, and there is practically no “white” rental market, there are no real tools that could increase the mobility of citizens.

“Solving the traffic congestion problem and making life acceptable to everyone requires a long-term city plan that takes into account more than just the traffic situation,” says Dorn. - The logic of this plan will dictate how to build a transport system. And by endlessly adjusting to the current needs of motorists, in 10 years the problem can be aggravated, and it will become unrealistic to solve it."