I wanted to expand a bit on Andrew’s post and the P-I article that inspired it, “Sound Transit’s light rail plan may cut traffic 30%, says study“.
It may be that this article just sort of disperses into the ether, but if not, it’s likely we’ll see a war of projections. What’s important to remember is the extent to which these projections are dependent on a lot of outside assumptions.
At one extreme, the city and county could decide to let light rail wither on the vine, by not investing in bus, bike, or car access to the stations. By leaving zoning restrictions steady, they could minimize the number of people that can easily walk to stations. At the same time, if Sound Transit 2 goes down and legal shenanigans somehow bring down University Link, you’d deny LINK the network effects that will exponentially increase ridership. Externally, a large fall in gas prices and local economic downturn would also depress ridership.
On the other hand, local jurisdictions could reorient bus service to feed light rail, build streetcars, expand light rail liberally, build adequate parking at P&Rs, and upzone massively around stations to allow population and job growth there. If drivers experience tolls, congestion, and/or high gas prices, a lot of them will be looking for an alternative.
As it happens, due to Federal Transit Administration rules, the official LINK ridership projections are quite conservative because they don’t allow for upzoning. That’s one reason I was gratified to see this article in the P-I about the city’s attempt to revise 20-year old neighborhood development plans to accommodate light rail.