why does adding more traffic lanes doesn’t help to alleviate traffic congestion?
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Adding lanes draws more cars onto highways and roads, leading to the same congestion as before. This is called “induced demand”.
It’s theoretically possible to have enough lanes such that anyone who wants to drive can do so whenever they want without congestion. In large cities especially, this is functionally impossible as there is simply not enough physical space for all that road (see California’s 20+ lane highways).
Cars are simply far too inefficient spacewise. How traffic congestion is actually reduced is taking lanes away from cars and turning them into pure bus lanes, tram and train lines, bike lanes, and sidewalks. By encouraging people to use highly efficient public transit instead of a car, people that do still choose to drive will experience less congestion and will find roads generally more pleasant to use.
Adding more lanes to a road can help to alleviate traffic congestion, but it is not a guaranteed solution. This is because adding more lanes can actually increase the number of cars on the road, which can lead to more congestion in the long run. This is known as induced demand.
Imagine a road with two lanes that becomes very congested during rush hour. If you add a third lane to the road, more people might be attracted to using the road because it will seem less congested, even though the same number of cars are still using it. This can lead to the same level of congestion as before, or even worse congestion.
There are other factors that can contribute to traffic congestion as well, such as bottlenecks, accidents, and road construction. In order to truly alleviate traffic congestion, it is often necessary to address these issues and consider a range of solutions, such as improving public transportation, encouraging carpooling, and creating more efficient transportation networks.
Trying to solve a traffic problem by simply adding more lanes is only addressing the problem in the short term, without tackling the root cause of the problem itself, which tends to be a chronic lack of alternative and more efficient transportation methods.
Cars are large. *Very* large once you consider that the vast majority of the time they’re only transporting one person, despite the fact that they typically have seating for 4-5 people. Anytime you’re driving, take a look at all the cars around you, and imagine that only a single person is standing wherever you see a car, and you’ll begin to see the problem.
Simply adding more lanes does nothing to address the fact that all of these people are choosing an extremely space-inefficient method of transportation. If traffic is to truly be solved, a much more comprehensive solution is necessary: trains, trams, buses, cycling, and walking should all be considered just as important as the automobile if a city is serious about tackling the issue of traffic once and for all.
A lot of people have mentioned induced demand, and that’s a huge part of it, but there’s another interesting part I don’t see people talking about: intersections.
If traffic is stopped, more road space is just more parking spaces and that doesn’t move anything through any faster. (It doesn’t even hold they many cars since they each take so much space). A road can technically handle a lot of traffic. Backups are caused by how many cars can get through the intersection at a time. More lanes can let more cars though the intersection, and it can also make intersections more complicated in ways that offset that.
This is why public transit can help so much with traffic. If you need to get 30 people though an intersection, you can send them through in 20 cars, or one bus. One of those clears much faster. Trains and trams can be set up to not have to negotiate intersections at all. Bike and pedestrian infrastructure gets way more throughout per land area since each person takes so much less space in the intersection and people can slip past each other easily.
If you had two towns with a population of 500 people each connected by a 2 lane road, and you expanded that road to a 12 lane superhighway? Then yeah, you got rid of traffic congestion. But it was crazy expensive and ultra wasteful. You would never expand it by that much, because you can’t afford it.
Let’s say I’m living in some city. I currently have a half hour commute, and I’m looking to move somewhere else in the same city. Like it would be nice to move into one of those new neighborhoods on the outskirts of town. Now if moving there means my commute goes from 30 minutes to 90 minutes… well then I’m probably not going to move. But if they widen the road from that neighborhood, and now the commute is only 45 minutes? Yeah I’ll move. So will a lot of other people though. So 5 years down the road, that wider road is handling a lot more traffic, so my commute is back to the 90 minutes it was originally.
The gist of it is, whenever people get in their car, or think about getting in their car, they take traffic into account. The other day I was going to go get a chocolate shake from a local fast food place, but I knew it was rush hour traffic and a drive of less than a mile was gonna take like 30 minutes, so I decided to wait. When you think about traffic, there’s a certain point where you say to yourself “no, that takes too long” and you do something else instead. We do that when we think about going to a restaurant, or when we think about buying a house in a new spot, really any time we think about driving. And that amount of time where you say “that takes too long” *doesn’t really change*. The thing is, it’s not just you. It’s all the other drivers as well. So if they add an extra lane, yeah you can get there 10 minutes faster. But then you and 300 *other* a-holes all decide that you’re okay with sitting in traffic for that shorter period. They don’t stop until it takes too long again.
The only way to decrease the traffic is for people to decide to stay home and not get on the road. Or to build so many lanes than you go broke. But eventually if enough new people move to the area, you managed to fill it up.
More lanes aren’t the answer. You need more exits. But not just more. You need exits in places that make sense which offer different ways to get to the places people want to go. And then you have to convince people to use the new exits and not the same one they have always used.
More lanes just means more cars in the same spot. Without more exits you still get more in than out.
Think of it like a sprinkler. It doesn’t matter how much bigger you make the hose if the sprinkler is only letting so much water through at once.
it absolutely alleviates congestion. They added a couple lanes to the beltway here – made things much better
People are comparing traffic demand to things like blood flow etc, but it’s important to understand scope, demand, inconsistency and how many lanes mean an improvement.
First: Demand. In a highly populated area there is a higher need for a larger amount of people to do something at one time. A seven lane highway will likely be pretty clear at 3am when most people are asleep, but in our human society we like to do things at the same time and have set schedules. That means that there are many magnitudes larger traffic demands at different times. The real question is how well the system can sustain strain.
What happens it that they will take a 4 lane highway make it 8 lanes. But, if the traffic at 5pm is 10 times larger than what it is at normal, then they have only helped to give twice as much area for the same amount of cars to take up. This might lead to traffic moving at a crawl for half the amount of time over all, but that effect isn’t going to make that large of a difference because the fact that the traffic is there is what is causing the stand still. Which means that it’s also unlikely that the traffic clearing in half the amount of time makes much of a practical difference.
This is part of the reason why transit systems that can handle large volumes of people without needing to take up tons of space (having an 8 lane highway is a lot of land to be taken up to get someone from point A to point B) are critical is highly dense populated areas like a city. It’s basically impossible for roads to keep up with volume because no matter what it’s a period of time where the infrastructure is unable to accommodate the demands and then grinds to a halt.
if you builfd it they will come
if youv got a quaint singl lane road through countrieside it will remain quaint and not very many cars
if you build a 6 lane highway through the same area, sure enough LA traffic
I once saw a YouTube video where they compared traffic to ants, and explained why ants don’t get stuck in traffic jams. They seemed to suggest that traffic’s mainly caused by impatient drivers trying to change lanes constantly and cut in front of each other (whereas ants don’t have this since they work together). I guess adding lanes helps a bit, but also means more lanes for people to move around in and slow things down for everyone else.
I would also assume that if a road’s already at or near capacity, adding more lanes would just attract more people from other roads to use this one.
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