Widening highways does not reduce air pollution, even if it reduced congestion, which it doesn’t. The only way to reduce air pollution from cars is to not drive them.
Reducing traffic jams certainly does decrease air pollution, assuming traffic remains the same. Given that traffic will nevertheless less remain horrific, Massachusetts has one of the better transit systems in the US, the recent transit zoning law, recent trends toward improving roads by reducing lanes and removing bottlenecks, and there’s at least $2B going to transit/cycling/walkability, there’s every chance traffic won’t increase.
Like, I’m thinking from my understanding of traffic and physics here. Lower speeds = more car density = more vehicles on a given stretch of highway, but also lower speeds = lower fuel consumption = less emissions/smog.
So if you had 100 cars driving down the highway, and 100 cars idling, the cars not in the traffic jam would emit more smog.
Traffic jams just emit a lot of smog because it’s when there’s the most amount of cars on the road.
Adding a new traffic lane = more speed and more cars = tons of smog
In a traffic jam your car may only be idling but you’re making zero mph. Acceleration/braking both hurt efficiency, but that’s all stop and go traffic is.
In MA, one of the projects in the “Bridge” section are the bridges to Cape Cod. They are a bottleneck partly for very narrow lanes. I believe the replacement project is for the same number of lanes plus a bike lane but modern standards will remove the bottleneck. Anyhow, during summer, it’s very common for Friday after work to have 40+ mile traffic jams. Spending extra hours in stop and go traffic to make the same trip clearly hurts efficiency and air pollution of over just getting there.
Before anyone chimes in with it will just increase traffic - this is already constrained by the number of rentals available and limits on development on the Cape. There would be no place for more tourists to go
Widening a bridge will increase traffic. 1 car households will turn into 2 or 3 car households as people decide to drive instead of taking the train or walking.
Development limits are meaningless. Traffic is not caused by population, but by car usage. Tokyo is the biggest city in the world, but it has almost no traffic.
Barnstable County has 230k people living in it. It is not physically possible to build a bridge that will move tens of thousands of cars during rush hour. Unless you live in the middle of nowhere, peak car traffic will always be constained by the roads, not the population.
So if you had 100 cars driving down the highway, and 100 cars idling, the cars not in the traffic jam would emit more smog.
They emit more, but emit less per mile. Idling means they’re emitting a low level all the time just sitting there for zero miles traveled.
It could be even worse if it’s not idle, but rather start and stop. Engines emit a lot more when they’re accelerating up, and a lot less while cruising.
Emissions per mile still go down. It is always more efficient per mile to drive at 40 mph than 60 mph, even if it takes longer.
Idling is negliable compared to the energy lost to air resistance.
Start-stop is a bit complicated, but it can be eliminated with hybrid vehicles and better trained drivers who understand how to drive in high traffic situations.
Also, people generally limit their trips by time, not by distance. This is related to induced demand, but if you increase the average car speed on a route, then those cars will just drive farther. If you live in a place with traffic and spend 15 minutes to get to the grocery store, then you’ll only go to grocery stores nearby. If you don’t have traffic, then you might drive the extra 5 miles to get to the cheaper grocery store on the other side of town. So the average engine run time does not go down when you reduce traffic.
Again, hybrid cars are actually more efficient in that kind of traffic than at 40+ mph, and those sorts of traffic waves are usually caused by bad drivers not knowing how to react to road congestion.
But sure, if people are regularly driving in stop and go traffic in a fully gas car, then I guess the pollution is worse than 40 mph. Adding new lanes would massively increase pollution due to the induced demand. There are more effective and cheaper ways to reduce traffic and pollution than to double the capacity of the road.
Widening highways does not reduce air pollution, even if it reduced congestion, which it doesn’t. The only way to reduce air pollution from cars is to not drive them.
Reducing traffic jams certainly does decrease air pollution, assuming traffic remains the same. Given that traffic will nevertheless less remain horrific, Massachusetts has one of the better transit systems in the US, the recent transit zoning law, recent trends toward improving roads by reducing lanes and removing bottlenecks, and there’s at least $2B going to transit/cycling/walkability, there’s every chance traffic won’t increase.
Is there a source that says this?
Like, I’m thinking from my understanding of traffic and physics here. Lower speeds = more car density = more vehicles on a given stretch of highway, but also lower speeds = lower fuel consumption = less emissions/smog.
So if you had 100 cars driving down the highway, and 100 cars idling, the cars not in the traffic jam would emit more smog.
Traffic jams just emit a lot of smog because it’s when there’s the most amount of cars on the road.
Adding a new traffic lane = more speed and more cars = tons of smog
In a traffic jam your car may only be idling but you’re making zero mph. Acceleration/braking both hurt efficiency, but that’s all stop and go traffic is.
In MA, one of the projects in the “Bridge” section are the bridges to Cape Cod. They are a bottleneck partly for very narrow lanes. I believe the replacement project is for the same number of lanes plus a bike lane but modern standards will remove the bottleneck. Anyhow, during summer, it’s very common for Friday after work to have 40+ mile traffic jams. Spending extra hours in stop and go traffic to make the same trip clearly hurts efficiency and air pollution of over just getting there.
Before anyone chimes in with it will just increase traffic - this is already constrained by the number of rentals available and limits on development on the Cape. There would be no place for more tourists to go
Widening a bridge will increase traffic. 1 car households will turn into 2 or 3 car households as people decide to drive instead of taking the train or walking.
Development limits are meaningless. Traffic is not caused by population, but by car usage. Tokyo is the biggest city in the world, but it has almost no traffic.
Barnstable County has 230k people living in it. It is not physically possible to build a bridge that will move tens of thousands of cars during rush hour. Unless you live in the middle of nowhere, peak car traffic will always be constained by the roads, not the population.
They emit more, but emit less per mile. Idling means they’re emitting a low level all the time just sitting there for zero miles traveled.
It could be even worse if it’s not idle, but rather start and stop. Engines emit a lot more when they’re accelerating up, and a lot less while cruising.
Emissions per mile still go down. It is always more efficient per mile to drive at 40 mph than 60 mph, even if it takes longer.
Idling is negliable compared to the energy lost to air resistance.
Start-stop is a bit complicated, but it can be eliminated with hybrid vehicles and better trained drivers who understand how to drive in high traffic situations.
Also, people generally limit their trips by time, not by distance. This is related to induced demand, but if you increase the average car speed on a route, then those cars will just drive farther. If you live in a place with traffic and spend 15 minutes to get to the grocery store, then you’ll only go to grocery stores nearby. If you don’t have traffic, then you might drive the extra 5 miles to get to the cheaper grocery store on the other side of town. So the average engine run time does not go down when you reduce traffic.
Traffic jams don’t go 40mph. They go up to 15mph and then back down to close to zero and back up to 15mph. That’s absolutely horrible for emissions.
Again, hybrid cars are actually more efficient in that kind of traffic than at 40+ mph, and those sorts of traffic waves are usually caused by bad drivers not knowing how to react to road congestion.
But sure, if people are regularly driving in stop and go traffic in a fully gas car, then I guess the pollution is worse than 40 mph. Adding new lanes would massively increase pollution due to the induced demand. There are more effective and cheaper ways to reduce traffic and pollution than to double the capacity of the road.
LOL, you ninja edited your post to add that part about start-stop and then acted like it’s my fault for not seeing it.
I dont blame you for anything, sorry about the confusion around expanding my comment.