DC’s current car trip reduction goal is woefully inadequate

This post is the second in an ongoing series about reducing the trips people take by car in DC. Read Part I here.

Reducing trips that people take by car in the District of Columbia would turn around our failure to achieve Vision Zero. In the first post of this series, I outlined why this is the case.

The good news is that DC already has a car trip reduction goal. The bad news is that it’s definitely not going to cut it.

DC’s car trip reduction goal

DC’s car trip reduction goal was originally stated in the Sustainable DC plan in 2012, which was updated in 2019 (that’s Sustainable DC 2.0). Starting from a 2011 baseline of 43.1%, the District aims to bring commuter trips made by car, including taxi and ride hailing, down to 25% by 2032—a targeted relative change of 42%. Translated into raw trips, that would be the equivalent of replacing over 72,000 daily commute car trips, based on an estimated 2011 baseline.

But that 72,000 is overstating it. Because the goal is expressed as a percentage rather than an absolute number of trips, it does not account for population growth. DC already has ~100,000 more residents than 2011, and by 2032 we are expecting another ~150,000+ more. Adding in that population growth, the 72,000 net reduction shrinks down to only ~27,000 fewer daily commute trips than the 2011 baseline. That’s a problem: The absolute number of trips is what matters most from a climate and safety standpoint.

Of course, it’s not just DC residents who drive on DC streets, and this goal’s singular focus on District residents is sub-optimal. That’s a limitation of the Census data that most easily powers this tracking, but it’s also not disqualifying.

As the physical and economic core of the region, DC wields significant influence on its neighbors. Aside from generally encouraging other jurisdictions to set and adjust their own goals, District policies to incentivize walking, taking transit, and biking over driving will necessarily impact the transportation choices of all users. If DC can induce its own residents to drive less on its streets, visitors will follow.

Breaking the commute bottleneck

A larger rub is that commute trips are obviously not the only trips that residents make. Commute mode share dominates our thinking about transportation systems because it’s a known quantity–it’s measured in Census surveys which are easily accessible to planners. But the reality is that commute trips represent only 21.4% of all of the trips that occur in DC.

The best pre-pandemic data publicly available is from 2017/2018 and shows that Washingtonians take just over 3 trips per person per day and use a car for about half of them, meaning DC crossed 1,000,000 trips taken by residents by car per day right around those years. If the aforementioned ~150,000 new residents adopt the same driving habits, they will add an additional ~250,000 more car trips per day by 2032. In that context, shifting the minority of commute trips by a few points is not going to cut it; those marginal reductions are completely overwhelmed by the raw volume of non-commute trips.

That’s a lot of math, but the bottom line is this: DC’s current modeshare target actually expects a net increase of ~150,000 car trips per day (against a 2018 baseline). This increase is fundamentally incompatible with our climate and safety goals.

The severity of the problem becomes even more clear when you compare it to another goal the District has already committed itself to: our Carbon Free 2050 plan to reach net zero emissions by 2050. That plan is targeting a reduction of 800,000 metric tons of annual emissions from the District’s transportation sector. To get there, the plan expects 500,000 metric tons of that target, or 62.5% of the total, to come from people switching from driving to taking the bus, biking, and walking.

An effective target

We will not prevent people from being killed by drivers or mitigate climate change with a net increase in trips. It’s clear these two goals were set without any alignment between the two, and are on a collision course for failure. (A problem that other jurisdictions like California are realizing, too). To bring them in line, the District should readjust its projections to move beyond just commute trips.

I propose that the Sustainable DC 2.0 goal be extended: Instead of 75% of commute trips via non-car modes, 75% of all trips should be made by non-car modes by 2032. Then, the District would be targeting a real, meaningful net drop of nearly 400,000 car trips a day, even accounting for expected population growth.

To be clear, the exact trip numbers here are not calculated with particular precision. I have taken a few publicly available data points and straight-lined them to create ballpark estimates. Professional planners could, and should, improve this with more rigorous analysis. But such rigorous analysis would still conclude that massive car-trip reduction is the only path to carbon neutrality and Vision Zero in the District.

A 75% all-trip goal by 2032 is a clear, understandable marker at the right order of magnitude. And it puts DC on pace to achieve its Carbon Free 2050 goals, which will require the District to reduce the absolute number of vehicle trips even further.