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Comment by ronbenton | Hacker News Reader

I took a transportation engineering class a while back and one bit of knowledge that stuck with me is tolls are the only effective traffic relief mechanisms for a roadway. Other mechanisms like adding lanes just invite more cars and traffic is not relieved. I never checked whether this was true, but sounded reasonable.

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Former transportation engineering prof here. This is exactly right. And for many transportation engineers, it's a reason to support toll lanes and to oppose adding (other) lanes. But I agree with some of the other commenters here, that adding lanes supports greater movement of people and goods and, separately, that toll lanes are regressive and come with plenty of (other) issues that are often ignored. My personal take on this is that toll lanes and congestion charging are the most effective methods we know for relieving congestion BUT that they are an incredibly difficult sell politically and maybe for good reason; maybe their issue are worse than the congestion they mitigate.

Thank you for your perspective. May I ask why you don’t still teach? I have always been fascinated by the idea of being a professor but never had the dedication to get a phd

I had a 3 year appointment overseas and could only get similar offers for my next job and only in places I didn't really want to live. Also my father was a professor and, to be honest, it was hard not to notice how much worse the job had gotten. Started to seem like twice the work for 10 or 20 percent of the salary and impact, as compared to tech. Also I was starting to have misgivings about transportation engineering as a field. So I guess just a lot. But I do miss the freedom to research what I thought was important. And teaching too. Honestly, academic jobs are more appealing to me now, in terms of lifestyle fit, than they were previously. I still apply for academic jobs occasionally but lately haven't gotten close to getting one. Don't get me started on the academic job market or application process. Ha!

Adding lanes may not cut congestion in the long term, but it can increase throughput and overall utility by moving more people and goods.

I don't doubt it. It is quite a while ago so I don't fully recall the talk that my professor gave, but I don't believe he intended to mean adding lanes was useless, just that they didn't help with congestion of the particular roadway

If adding lanes doesn't help you didn't add enough. People live in a city to do things and you need to enable that by preventing congestion.

i don't know how to afford the 50 more lanes that most cities need though. I suggest better transit.

Removing parts of the city to add more lanes will also help decreasing demand - it's a win-win!

Each additional lane has less and less impact because of lane switching. Ultimately, you can still only enter or exit on the left or right, regardless of if you have 100 lanes. And having people move across 100 lanes to exit is much slower than moving across one or two.

    > Other mechanisms like adding lanes just invite more cars and traffic is not relieved.

I have been seeing this argument for 30 years, and, yet, rich cities in the US (and Canada) continue to add more lanes. My guess: It is just so politically positive to build more lanes that politicians continue to approve them. Why doesn't this happen as much in other rich countries?

It’s just supply and demand.

Of course just creating more supply when the cost to the consumer is basically 0 will just juice the demand to fit the new capacity. Tale as old as time.

But you run into the risk that people don't use your new expensive toll road and you're left with a big pile of debt...

That is the problem with them in the Netherlands. Building and maintaining roads is so frighteningly expensive that you can't price them to even cover the cost!

I think perhaps my professor was talking about adding tolls explicitly as a traffic congestion relief mechanism rather than a way to recoup cost of maintaining the roadway

So you mean if we dont socialize the up-front cost plus the ongoing externalities, roads aren't economically sensible choice? That seems less like a problem and more like the beginning of a nice reflection...

No form of transportation would be at that point

Have you considered fuel rationing?

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