Drunk driving is a serious problem throughout the United States, and that is particularly true in Pennsylvania, which is the fourth-highest state for DUI fatalities even though its population is only sixth-highest in the country. In Pennsylvania, alcohol-related motor vehicle deaths exceed the national average by 24%, and alcohol is responsible for 38% of all motor vehicle fatalities—one of the highest rates in the nation.

Last month, Pittsburgh resident and blogger Nate Good caught our eye when he posted an analysis of drunk driving in the Philadelphia area, which demonstrated that DUI rates have fallen in the city since Uber’s arrival. We previously tested this theory in Seattle and found a causal relationship between Uber arriving and DUI rates falling by about 10%. Good’s analysis begins to provide evidence to support this theory. But, of course, correlation is not causation—other factors could be contributing to falling DUI rates too.

However, we’re big believers that if you give people a safe, affordable, and convenient alternative to drinking and driving, fewer people will drive drunk. So, while Uber is still new to the state of Pennsylvania, we expect to see a huge impact here.

Let’s take a look at some data to understand why.

1. Uber Requests from Pittsburgh & Philly Bars Over-Index 3-5X

First, we can look at what kinds of establishments Uber users request cars from. For example, some users request trips from bars, others from restaurants. We can compare the percentage of requests from bars to the overall percentage of establishments that are bars.

Here is our finding: Requests for rides come from Uber users at bars at a much higher rate than you might expect based on the number of bars there are in the city. Requests from users at bars are between three and five times greater than the total number of bars would predict. In cities lacking reliable transportation alternatives, like Pittsburgh and Philadelphia, Uber is a reliable way to get home from bars, and our users know this.

2. Drunk Driving Fatalities Happen More at Night, and on Weekends

Next, we took a look at days and times drunk driving most often occurs throughout the week. Government data is available at the national level, and here’s a (smoothed) chart of DUI fatalities at the national level by time of day. The report indicates that weekends are particularly dangerous for DUI fatalities, though it doesn’t provide direct data.More than 60% of DUI fatalities occur at night, and 12 to 3 am is the peak three-hour period for DUI fatalities. This pattern is true for the state of Pennsylvania as well. Data from the state crash facts and statistics report shows: 74% of the alcohol-related crashes in PA were during the hours of darkness, usually on weekends. The interval when the highest incidence of drunk driving crashes takes place: midnight to 3:59 AM on Sundays.

3. Uber Ride Requests in Pittsburgh and Philly Peak on Weekend Nights, Especially after Last Call

Let’s take a look at the distribution of Uber’s trip requests over the course of a week in Pittsburgh and in Philadelphia:

Two things jump out: Trip requests spike at night, and they spike on weekends—the times when DUIs are the biggest problem. (We also noticed that requests super-spiked at 2 AM Sunday morning in Pittsburgh—this makes intuitive sense, as Pittsburgh has the most bars per capita in the nation, at 11.8 per 10,000 people, and has been largely underserved by reliable transportation alternatives.)

Let’s look at this a little more closely, keeping in mind that bars in both Pittsburgh and Philadelphia close at 2 AM. Starting with Pittsburgh:

The data in Philadelphia tells a similar story, that Uber users really want a ride home from the bars at closing time:Users want to rely on Uber to get them home from the bar safely. If even a small number of these users might have driven in the absence of a reliable ride home, then it’s safe to conclude that Uber can and will take drunk drivers off the road.

We’re really proud to provide a safe, reliable transportation option in Pennsylvania. It’s amazing to think that by offering a convenient way to get home from a night out Uber is contributing to the reduction of drunk driving in cities like Pittsburgh and Philadelphia.

We recently partnered with Mothers Against Drunk Driving to help keep our roads safe over the July 4th holiday. Safety is our absolute number one priority, so having some data to show that we’re helping to make a difference is extremely rewarding.