Part 2 in a (now?) series of posts analyzing Capital Bikeshare usage data. This post focuses on system-level usage by trip duration. See parts 1, 3, and 4, 5, 6, 7 (maps of travel patterns), 8, 9 (weather).
When Capital Bikeshare riders get on those big red bikes, how long do they keep the bike out? Are most trips for a 5-minute jaunt to Dunkin’ Donuts where you’re too lazy or hurried to walk? Or are these longer trips?
Here’s a frequency distribution of all 1.36 million trips, grouped into buckets of 2 minutes each, casual and registered users alike. For trips lasting more than 60 minutes, way out on the right of the graph, I started grouping rides in larger chunks of half-hours and hours. (Zero and below is bad data).
The single most popular trip duration for all users is 4-6 minutes, followed by, surprisingly, 10-12 minutes. That would suggest that alot of users are riding for short (like, 1 mile) trips, but also hints that there may be two sub-markets here (would need to break this down by geography and time of day).
The vast majority of trips (88%) are less than 30 minutes. At first, I figured that meant that registered users are just savvy and are watching the clock to avoid fees. But, there isn’t a steep dropoff right at 28 or 30 minutes. In fact, there have been more rides between 30-32 minutes (barely incurring fees), than 28-30 minutes (just under the limit of free time). Instead, maybe 20 or 25 minutes (roughly 2, maybe 3 miles?) is just the maximum amount that average users are willing to ride. Anything longer, and they’ll choose another mode. Or, it could be that with 2 or 3 miles you can just get to most things in the D.C. and Arlington core. Or both. What do you think?
Also, what’s up with the casual users? The distribution of their trip lengths is really different. Let’s look at that same graph, but withe casual users only:
The distribution is much more even – only 59% of trips are under the 30-minute threshold. For casual users, 40% of all trips exceed the 30 minutes and incur fees. And, there’s a big spike of hour-plus usage for casual users. 23% of their trips are 60 minutes or more. It seems that a good chunk of casual users are also using the bikes for 1, 2, even 3 hours. Are these tourists riding around the monuments all afternoon, perhaps caught near the Tidal Basin and far from a station? Are they inelastic to (or unaware of?) the fees that start rolling in after 30 minutes? Will this tail tend to drop off as new stations are installed on the Mall?
Does trip duration change by season? Does winter’s bitter cold keep rides short? Here’s the same frequency distribution, but broken down by season (I couldn’t fit user type on there too).
Turns out, the distribution of trip durations stays pretty constant by season. As use declines in the winter, it declines across all trip lengths, and vice versa in warmer weather. There’s a pretty consistent spike of use around the 5-minute mark, and then again in the 10-12 minute mark. And, the “tail” of hour-plus rentals is biggest in the summer and spring, but still persists a little in the winter too.
How is this useful? While it’s hard (but possible) to make inferences about where riders go or what path they take (although OObrien is doing a great job), knowing the length of the rental might help estimate distance traveled. Especially in cases where return station is same as rental station, or where imputed speed is so low that there must’ve been a pitstop or a loop.
More to come next week, stay tuned. I’d like to explore station-to-station link data, usage vs. capacity, and the effects of weather. One thing that would help is a way to group the stations into zones or neighborhoods – reducing the number of station-to-station pairs might help visualize flows. Any good ideas?