I’m seeing a significant and consistent discrepancy between travel time estimates from Valhalla (using OpenStreetMap data) and Google Maps, and I’m trying to understand what might be causing it.

I expect some variation due to factors like traffic, road conditions, or differing assumptions, but the magnitude and pattern of the difference seem too large to be explained by those alone.

Example

Route:

• Start: 52.23564716272248, -0.8956605756449354
• End: 52.07597901967018, -1.0213206533329537
• Distance: ~30 km (UK)

Results:

• Valhalla (via https://valhalla.openstreetmap.de): ~58 minutes
• Google Maps: ~33 minutes
• Mapcarta (also OSM-based): ~33 minutes

Observations

• Valhalla consistently gives significantly higher travel times than Google Maps.
• The discrepancy is large (in this case, ~75% longer).
• This is not a one-off case. I’m observing a consistent trend where the gap increases with route distance. This chart shows this trend - you can see that the disagreement between Google and Valhalla increases with increase in distance.

https://preview.redd.it/t4vgmej2qbyg1.png?width=1181&format=png&auto=webp&s=2105bbf13305c49803bc9e064b01aec978861a3a

• Another OSM-based service (Mapcarta) produces estimates much closer to Google Maps.

Question

Given that both Valhalla and Mapcarta rely on OpenStreetMap data, what could explain such a large and consistent difference in travel time estimates?