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Ive seen multiple sources say that widening roads only makes the problem worse yet in this article and in your comment it seems like the "solution" people are g

Ive seen multiple sources say that widening roads only makes the problem worse yet in this article and in your comment it seems like the "solution" people are going for. That leaves me wondering; Are these sources not sound or are the people in charge of transport morons?

bsder 9y ago
Define "makes the problem worse". More lanes, in networking terms, improves throughput but doesn't improve latency. More lanes moves more cars. That's fairly straightforward. More lanes doesn't improve the time of an individual commute on the road or cut down on congestion of the road. People have a fixed annoyance level, and congestion will increase until that annoyance level equilibrium is reached again. The only time more lanes genuinely improves things is when the extra lanes suddenly means that the road now has more capacity than required to carry the traffic level it sees. Normally, the cost required to add that many lanes is sufficiently prohibitive that such a situation almost never occurs.
- adrianN 9y ago
  More lanes also induce more demand. Plus there is this https://en.wikipedia.org/wiki/Braess%27s_paradox https://en.wikipedia.org/wiki/Braess%27s_paradox
scythe 9y ago
There are a few cases where widening roads actually does make traffic jams worse (Braess' paradox), but in the majority of cases, wider roads make traffic flow better, but more traffic flows, which makes the benefit smaller than what you'd expect if the same number of cars were on the road. It's debatable whether the increased traffic flow is an undesirable side effect or represents an increase in public utility.
toast0 9y ago
When people say widening roads makes the problem worse, they usually cite as an example 'before construction, traffic was congested for X minutes; and after it is congested for X + Y minutes' the problem is that often demand has increased in the meantime (because of population growth, or increased economic activity). There is certainly some amount of induced demand, and in the right scenarios, that could make things significantly worse. In the Bay Area, if 880 was significantly widened but 101 and 280 were not, it might make it attractive to drive from San Francisco to San Jose by crossing the bay and taking 880 south. This could make 880 less effective for east bay users. This doesn't become a significant issue if there's reasonable regional planning, and routes are kept in rough balance. There's a limited budget for transportation projects though, and they can be complex and time consuming, so often roads aren't widened until there is a significant amount of peak congestion. During construction, things get worse, and afterwards, there's still a period of peak congestion. People who expect a road widening to create free flow conditions at all hours will be sorely disappointed. I'll add that on and off ramp design makes a big difference in traffic flow as well; a full clover leaf is good for interchanges with low traffic, but all the weaving makes for poor results in congestion; redesigning to avoid weaving helps flow tremendously without widening, although more/different space can be needed depending on the specific road alignment. There is potential to argue about what is the best use of transportation money; I'm not familiar with transportation in the DC area though, so I won't weigh in on that.
megablast 9y ago
If all you have is a hammer... Australia cities are dominated by cars, people can't imagine a world with them, even the cities are cars first. It is a joke.

bsder 9y ago

Define "makes the problem worse". More lanes, in networking terms, improves throughput but doesn't improve latency. More lanes moves more cars. That's fairly straightforward. More lanes doesn't improve the time of an individual commute on the road or cut down on congestion of the road. People have a fixed annoyance level, and congestion will increase until that annoyance level equilibrium is reached again. The only time more lanes genuinely improves things is when the extra lanes suddenly means that the road now has more capacity than required to carry the traffic level it sees. Normally, the cost required to add that many lanes is sufficiently prohibitive that such a situation almost never occurs.

adrianN 9y ago
More lanes also induce more demand. Plus there is this https://en.wikipedia.org/wiki/Braess%27s_paradox https://en.wikipedia.org/wiki/Braess%27s_paradox

scythe 9y ago

There are a few cases where widening roads actually does make traffic jams worse (Braess' paradox), but in the majority of cases, wider roads make traffic flow better, but more traffic flows, which makes the benefit smaller than what you'd expect if the same number of cars were on the road. It's debatable whether the increased traffic flow is an undesirable side effect or represents an increase in public utility.

toast0 9y ago

When people say widening roads makes the problem worse, they usually cite as an example 'before construction, traffic was congested for X minutes; and after it is congested for X + Y minutes' the problem is that often demand has increased in the meantime (because of population growth, or increased economic activity). There is certainly some amount of induced demand, and in the right scenarios, that could make things significantly worse. In the Bay Area, if 880 was significantly widened but 101 and 280 were not, it might make it attractive to drive from San Francisco to San Jose by crossing the bay and taking 880 south. This could make 880 less effective for east bay users. This doesn't become a significant issue if there's reasonable regional planning, and routes are kept in rough balance. There's a limited budget for transportation projects though, and they can be complex and time consuming, so often roads aren't widened until there is a significant amount of peak congestion. During construction, things get worse, and afterwards, there's still a period of peak congestion. People who expect a road widening to create free flow conditions at all hours will be sorely disappointed. I'll add that on and off ramp design makes a big difference in traffic flow as well; a full clover leaf is good for interchanges with low traffic, but all the weaving makes for poor results in congestion; redesigning to avoid weaving helps flow tremendously without widening, although more/different space can be needed depending on the specific road alignment. There is potential to argue about what is the best use of transportation money; I'm not familiar with transportation in the DC area though, so I won't weigh in on that.

megablast 9y ago

If all you have is a hammer... Australia cities are dominated by cars, people can't imagine a world with them, even the cities are cars first. It is a joke.