SafeRide by the numbers
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    It’s 1 a.m. on Thursday night, and you just got back from a wild night at formal. Bad decisions have led to even worse ones, and that means Burger King. You fumble with your phone trying to hail a SafeRide as you dream of Whoppers and fries and those super size drinks as big as your head. You wait and you wait, but by the time that white Prius arrives, the call of your bed is stronger than that of the King.

    Yet that wait should be shorter than ever before. About a year ago, SafeRide enacted two major changes: a policy change requiring rides to start or end on campus and the introduction of TapRide, an app which allows students to virtually request SafeRides. The question is whether these changes had any effect on wait times.

    Background

    The backlash against the policy change was considerable, with an online petition to bring back off-campus to off-campus rides garnering over 600 signatures. Interestingly enough, Evanston officials said that SafeRide was never in danger of being shut down for violating city codes (the main reason cited for the policy change). The public outcry overshadowed the simultaneous release of TapRide, the app which promised to considerably reduce wait times for SafeRide.

    Both TapRide and the policy change debuted on April 1, 2014 with the start of Spring Quarter 2014. According to Julie Payne-Kirchmeier, assistant vice president of student auxiliary services, SafeRide wait times decreased two weeks after the policy went into effect. She said that releasing the app in conjunction with the policy change was always the plan.

    SafeRide's Facebook and Twitter provide a more detailed picture. Since 2009, SafeRide dispatchers have been posting estimated wait times every night, all the while advancing their careers as budding comedians.

    Data

    Compiling tweets from the last three years, we end up with the following graph measuring the average wait time for each month.

    Production by Al Johri and Alex Duner. Note that June 2014 has two data points, reflecting the fact that June falls in both Spring and Summer Quarters.

    Starting with April 1 of last year, wait times plummeted. It’s difficult to infer whether the policy change or TapRide had a greater effect due to their concurrent release, but we can be sure of one thing: wait times dropped. According to a Daily Northwestern interview with SafeRide dispatchers, off-campus to off-campus used to take up the bulk of rides that SafeRide provide. We can speculate that the drop is primarily due to the policy change removing those rides.

    You’ll also notice the small segment of wait times between June and August 2014, which marked the first time SafeRide extended their service to the summer.

    It’s important to note that the average wait times are all sitting in the high 30’s because the average does not account for the number of times SafeRide was “overbooked.” After around a 40-minute wait time, SafeRide directs students to take the shuttle in order to prevent wait times from climbing sky-high.

    So, when is the best time to get a SafeRide?

    Production by Al Johri and Alex Duner.

    7 p.m. and 1 a.m. seem to be the clear winners here, while getting a safe ride at 11 p.m. seems nigh impossible. With all wait times this school year now below the 40-minute threshold, maybe the policy change was the right call after all.

    Methodology

    About 8000 tweets are included in this analysis. The data was obtained using a simple scraper because the Twitter streaming API has a maximum limit of 3,200 tweets. You can view the raw data in .csv form here. A series of tight regular expressions were used to extract the number of minutes from each tweet to minimize the number of false positives (tweets with numbers in them that aren’t actually a wait time; e.g. dates, days until end of the quarter, etc.). When SafeRide tweets out “open” or “last rides”/“booked” (along with its many synonyms), I assigned a wait time of 0 and infinity respectively. The infinity wait times were (obviously) not used in the averages. Because SafeRide stops accepting rides after a certain threshold wait time (around 40 minutes), we don’t see huge spikes in wait times on days that are perhaps unusually busy. Further analysis might look at how many times SafeRide gets “booked” or “overbooked” per day.

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