why does adding more traffic lanes doesn’t help to alleviate traffic congestion?
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I believe another huge part of it is the lack of education regarding highway rules and safety, at least in the US and Canada.
I know for a fact there are many drivers on the road who have “transferred” their license from another country. There are also a lot who pay to pass their driver’s test.
All these factors combined equal uneducated, ignorant, non-logical drivers. Many of whom do not match highway/freeway speed while merging. I witness a *lot* of people quite literally sitting in the passing lane(s).
Add in the fact that a majority of cargo delivery in NA is done through semi-trucks. It becomes a compound issue.
If everyone simply followed the logic “pass on the left, resume cruising on the right” there would be far less traffic. Additionally, some patience and consideration would be necessary.
Many have already answered well, however, if you want some visual representations, look up Braess’s Paradox on YouTube and you’ll be able to find many good videos helping to explain with visuals.
Edit: my recommended video https://youtu.be/cALezV_Fwi0
It’s not the lanes that cause traffic in most cases, it’s driver behavior. If everyone maintained their vehicle, went the actually speed limit, used their signal, paid attention to other people using their signal, paid attention to driving in general, left a safety gap between themselves and the vehicle in front of them, traffic would always be fairly pleasant.
I think it is also partially due to the fact that the systems are saturated with drivers or potential drivers.
If the road system is handling 150% of design capacity, adding 20% more does not make much of a dent as you are still running at 130%. It might even get worse as now more of the potential drivers take to the road (potential drivers being people that used to avoid driving or took alternate transport.)
Look at a freeway system like the 405, even at 3 am it can be bumper to bumper, and you would think a significant number of people would be asleep or at least in for the night.
You just can not build enough roadway with that density of humanity. Add to the fact that we still cram as many workers into the city center from the suburbs every day from 6am to 6 pm and you will always get gridlock.
I moved to the DC area (a huge metro with lots of suburbs) as Covid was ramping up. My commute should have been about 20 min, even with Covid ramping up, my commute was about 45 min. Once all the lockdowns went into effect, my commute was back down to 20 min and I only had any backups on poorly designed suburban roads.
Once people started to commute to work again, the times are back up till now that same commute is close to 60 min on a good day. The suburban routs that still had issues during Covid are almost undrivable.
Mass transit can only help so much, our cities are huge sprawles compared to cities with fewer issues and our population is dispersed. To get timely transit to enough people is very expensive (more per person then that person owning a car) and much of that infrastructure will sit idle or low volume for 12 – 16 hours a day. In addition, you will create traffic disruptions to the existing grid, displace people and businesses to build the new infrastructure, elevated costs to build, and doing all that while telling commuters they will need to give up their cars.
More lanes actually *do* help relieve congestion for a fixed amount of traffic, otherwise we’d save money by just building two lane roads everywhere. There are two primary issues that work against this. First, build better roads and more people will drive. But the second issue is worse – you have to get traffic on and off your big road. Typically, that only happens on the far right lane, sometimes the far left lane. Sometimes a couple of those lanes. People have to get to that one side to get off, and usually people get on on that same side. This causes congestion as the traffic mixes.
(Assuming an access-controlled highway. Normal surface streets have this and much more). Cars do not drive in a single lane straight down the highway for their whole trip. There is always entering/exiting the highway, which almost always requires merging into another lane. Merging and changing lanes causes cars to slow down, especially if the road is near saturation with other vehicles. If you add more lanes, that creates more merging/lane changing just to use them. Even if the far left HOV lane is moving, it will slow down the other lanes as vehicles have to cross them to get over. Imagine a 100lane wide road: cars would likely spend more time trying to get to the 100th lane than the normal trip in one lane would take to complete. Add in the behavior of people trying to merge early (causes the cars in the merging lane to slow down earlier and more, since this car is likely not up to speed) instead of zipper merging where the lane tells you to (cars are generally ready for the other vehicles to move in, and have the space available for them to and can maintain speed), or the other behavior of not allowing cars to merge (the refused car will likely move further ahead anyway and merge there, causing everyone behind this new merge point, still in front of the refuser, to slow down, possibly even more), and you get more extreme slowdowns regardless of how many lanes exist. Slowness in one lane often causes slowness in the neighboring lanes, again because cars have to merge between those lanes.
tl;rd: Cars have to change lanes, changing lanes causes slowdowns, adding lanes increases lane changes, increases the slowdowns after a certain point.
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