Some traffic engineers have maintained for years that the solution to road congestion is to just build more roads. And on its face, this sounds like a rational assumption – if a road is clogged with traffic, just make it bigger and the traffic will go away, right? Unfortunately, this perspective is short-sighted and fails to take into account the impacts that widened roads have on our health and quality of life through the increased traffic they bring.
Sure, after a road has been widened it may see reduced traffic for a while – but these congestion reductions are only temporary. Eventually, traffic will creep back up to normal levels or even surpass the volume seen before construction started. This is because of the concept of induced demand.
Although it’s hard to explain it as well as the gentleman above does, induced demand describes how when new roads are constructed (or roads are widened), city residents will adjust their behaviors to the improved conditions. With the new road space (and temporarily reduced congestion), they’ll take longer trips, they’ll travel further, and people who previously didn’t drive will feel motivated to start. However, when everyone does this, it just leads to the same congestion as before, only with even more cars driving on our roads and polluting our air. Ultimately, it boils down to basic economics – if you make it easier, cheaper, and more convenient to drive, more people are going to do it. And that’s exactly what we need to avoid.
There is ample evidence for this phenomenon spanning back decades – time and time again, cities learn that building new roads does not solve their traffic woes. But why do we still think that adding more lanes is the solution? Because city and state leaders, who are usually seeking reelection every 2 to 4 years, want to appear to constituents as if they are “solving the traffic problem,” that they are taking concrete action that can win them political points in time for the next election. And by the time the projects are complete and the evidence is on the table, they’re already out of office or they’re ready to advocate for further expansion. Wash, rinse, repeat.
The good news is that induced demand can work both ways – further investment in comprehensive bike networks, more frequent transit, and pedestrian infrastructure does encourage people to use these environmentally-friendly options at higher rates. When we couple these infrastructure investments with density-friendly development policies that encourage walkability, we make our city easier to navigate while reducing the need for cars at all. But with limited budgets and limited time, it’s all the more essential that we invest now in the infrastructure that will give us the city we want 30 years from now. As cliché as it may sound, “if you build it, they will come” – and we need to make sure we’re building the right things.
Header photo by Ellen M. Banner