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I'd like to see a study across all road construction whether excessive induced demand is a guaranteed effect. In all articles related to it I only see examples

I'd like to see a study across all road construction whether excessive induced demand is a guaranteed effect. In all articles related to it I only see examples cherry-picked where induced demand negated the effects of adding lanes. However, it's not clear whether this is universally true, true enough to be a rule of thumb, or something that only occurs in specific situations. Anecdotally, removing toll plazas in favor of plate scanners and adding bridge lanes to the Goethals Bridge in Staten Island, as well as widening the Staten Island Expressway, has significantly reduced traffic delays and improved safety for several years. There _are_ more vehicles using the road but not enough more to significantly negate the improvements. https://www.panynj.gov/port-authority/en/press-room/press-release-archives/2020-press-releases/vehicle-crashes-decline-at-new-goethals-bridge-with-wider-lanes-.html https://www.panynj.gov/port-authority/en/press-room/press-re... To me, the case against improving roads is not nearly as open-and-shut as Strong Towns and similar one-sided policy-pushers make it out to be.

kiba 5y ago
It would seems that removing the toll booths dramatically increases capacity and safety without the need to add additional lanes. Also, more vehicles are using the road, true, but you have to remember that it increases over time.
- sempron64 5y ago
  How fast does demand grow? Does it ever stop or slow down? I know for a fact that far from every highway and road in America is congested: the majority are not. Even many if not most roads in metropolitan areas are not. So you can’t extrapolate demand increases ad infinitum for the current moment.
corin_ 5y ago
I don't know the data (or this area particularly well generally), but intuitively I would expect induced demand to be seen in the majority of cases of roads being updated for increased capacity. Not because of a necessity that any capacity increase must always cause it, but because the decisions of which roads to expand are made by humans who, with the exception of edge cases (maybe the reason for rebuilding was because of the state of the road and increased capacity was a secondary affect rather than the main motivation; maybe corruption led to a poor choice being made; maybe forward looking expecting future demand to increase years later based on other factors like planned new buildings) wouldn't spend money increase capacity unless road traffic has been increasing and looks like it is't about to start trending in the opposite direction soon enough to make expanding the road a pointless short-sighted exercise. Aka if increasing road capacity wouldn't induce more demand, how likely is it to be in a situation where it's considered worthwhile expanding it?

kiba 5y ago

It would seems that removing the toll booths dramatically increases capacity and safety without the need to add additional lanes. Also, more vehicles are using the road, true, but you have to remember that it increases over time.

sempron64 5y ago
How fast does demand grow? Does it ever stop or slow down? I know for a fact that far from every highway and road in America is congested: the majority are not. Even many if not most roads in metropolitan areas are not. So you can’t extrapolate demand increases ad infinitum for the current moment.

corin_ 5y ago

I don't know the data (or this area particularly well generally), but intuitively I would expect induced demand to be seen in the majority of cases of roads being updated for increased capacity. Not because of a necessity that any capacity increase must always cause it, but because the decisions of which roads to expand are made by humans who, with the exception of edge cases (maybe the reason for rebuilding was because of the state of the road and increased capacity was a secondary affect rather than the main motivation; maybe corruption led to a poor choice being made; maybe forward looking expecting future demand to increase years later based on other factors like planned new buildings) wouldn't spend money increase capacity unless road traffic has been increasing and looks like it is't about to start trending in the opposite direction soon enough to make expanding the road a pointless short-sighted exercise. Aka if increasing road capacity wouldn't induce more demand, how likely is it to be in a situation where it's considered worthwhile expanding it?