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Show HN: OpenTimes – Free travel times between U.S. Census geographies

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Re: Show HN: OpenTimes – Free travel times between U.S. Census geographies

#51

Post by zild3d »

dfsnow wrote: post #32
svcphr wrote: post #29

How did you decide on routing engine? I’ve used Graphhopper in the past — is OSRM an improvement?

I actually tried a couple different engines before landing on OSRM. I started with R5 (since it can also do public transit) then switched to Valhalla. The main limiting factor was speed. Basically all routing engines except for OSRM are too slow to compute continent-scale travel time matrices. For reference, it took Valhalla around a week to finish 3 billion point-to-point pairs. OSRM did the same calculation in abou…

Yeah OSRM precomputes routes so if you just need the same mode of transportation and not dynamic params (like avoid tolls on this route, etc) it's gonna be a lot faster. Valhalla was designed for flexible/dynamic routing

Re: Show HN: OpenTimes – Free travel times between U.S. Census geographies

#53

Post by modriano »

kalendos wrote: post #44
c_moscardi wrote: post #5

Amazing! GitHub actions to compute a giant skim matrix is an incredible hack. I pretty regularly work with social science researchers who have a need for something like this... will keep it in mind. For a bit we thought of setting something like this up within the Census Bureau, in fact. I have some stories about routing engines from my time there...

Totally! I've been using this pattern a lot and recently wrote about it. https://davidgasquez.com/community-level-open-data-infrastru...

Thank you for this excellent post! I've been developing [my own platform](https://github.com/MattTriano/analytics_data_where_house) that curates a data warehouse mostly of census and socrata datasets but I haven't really had a good way to share the products with anyone as it's a bit too heavyweight. I've been trying to find alternate solutions to that issue (I'm currently building out a much smaller [platform](https://github.com/MattTriano/fbi_cde_data) to process the FBI's NIBRS datasets), and your post has given me a few great implementations to study and experiment with.

Thanks!

Re: Show HN: OpenTimes – Free travel times between U.S. Census geographies

#54

Post by DennisL123 »

zild3d wrote: post #51
dfsnow wrote: post #32

Earlier quoted context omitted.

I actually tried a couple different engines before landing on OSRM. I started with R5 (since it can also do public transit) then switched to Valhalla. The main limiting factor was speed. Basically all routing engines except for OSRM are too slow to compute continent-scale travel time matrices. For reference, it took Valhalla around a week to finish 3 billion point-to-point pairs. OSRM did the same calculation in abou…

Yeah OSRM precomputes routes so if you just need the same mode of transportation and not dynamic params (like avoid tolls on this route, etc) it's gonna be a lot faster. Valhalla was designed for flexible/dynamic routing

It precomputes partial routes that are combined at run time. :)

Re: Show HN: OpenTimes – Free travel times between U.S. Census geographies

#55

Post by modriano »

philipodonnell wrote: post #37

Very cool! What did you use to make the ER diagram?

I'm not OP, but he used mermaid.js's Entity Relationship Diagram model [0]. GitHub renders it automatically [1].

[0] https://mermaid.js.org/syntax/entityRelationshipDiagram.html

[1] https://github.blog/developer-skills/github/include-diagrams...

Re: Show HN: OpenTimes – Free travel times between U.S. Census geographies

#56

Post by veilgen »

This is an impressive project! Providing free access to such a massive dataset of pre-computed travel times could be a game-changer for researchers and policymakers who rely on spatial accessibility data but often face high costs with commercial providers.

The technical approach is also fascinating—using static Parquet files on R2 instead of a traditional database keeps costs low while maintaining accessibility via SQL and DuckDB. Offloading computation to GitHub Actions is a clever way to handle large-scale processing efficiently.

It'll be interesting to see how this evolves, especially with the potential addition of traffic-aware travel times. Great work!

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