I’ve spend much of January improving arf’s performance. The 30-minute time budget access map for Washington state that used to take around 70 minutes now takes approximately 40 on my M1 2020 MacBook Air. A map of Seattle with the same parameters takes around eight. With the performance enhancements in place, I wanted to subject arf to a new trial: creating a 30 minute unweighted access map of New York City.
Relative amount of thirty-minute transit and walking access throughout New York City. Map data from OpenStreetMap.
It took an hour and seven minutes to generate the map above, notably more time than it takes to produce one for the much larger Washington state. In terms of sectors, the 80 square meter area units of arf’s computation, New York City is 3.32 times the size of Seattle, but a thirty-fifth of the size of Washington state. Many places in Washington are not within a half hour walk of any transit service, though, which results in an approximately 1000-fold decrease in computation time for these sectors. Some remote parts of New York City meet this criterion, but they are rare. Furthermore, New York City’s transit-richness, compared to Seattle, slows computation, since more routes, many with a greater number of trips, must be navigated.
Work is ongoing to optimize the transit pathfinding component of arf, which has largely not been touched since being ported over from the BusGraphs Access Analyzer. New York City is an excellent testbed for assessing future optimizations.
The following command generates the New York City access map at the beginning of the post:
arf access nyc --areas 175905 --duration 1800 --concurrency 8 --date 2026-01-22 --partitions 2 --reporters sectorcount --gtfs "https://rrgtfsfeeds.s3.amazonaws.com/gtfs_subway.zip,https://rrgtfsfeeds.s3.amazonaws.com/gtfs_bx.zip,https://rrgtfsfeeds.s3.amazonaws.com/gtfs_b.zip,https://rrgtfsfeeds.s3.amazonaws.com/gtfs_m.zip,https://rrgtfsfeeds.s3.amazonaws.com/gtfs_q.zip,https://rrgtfsfeeds.s3.amazonaws.com/gtfs_si.zip,https://rrgtfsfeeds.s3.amazonaws.com/gtfs_busco.zip,https://rrgtfsfeeds.s3.amazonaws.com/gtfslirr.zip,https://rrgtfsfeeds.s3.amazonaws.com/gtfsmnr.zip,https://nycferry.connexionz.net/rtt/public/utility/gtfs.aspx"