Excessive speed in the JSON response from OSRM map matching

[alex6H]

Hello,

I have searched for an already open discussion or issue but couldn't find the answer I was looking for.

I have map match a dataset of GPS tracks in a major town in Malawi using OSRM. In my URL request to OSRM, I send the coordinates and timestamps. It works well, except that in the JSON response (in matchings>leg > annotation > speed) , the speed for each OSM edge doesn't seem correct. The speeds can go up to 160 km/h on urban roads where it is not realistically possible (I know this because I was in the car during the track recording).

Initially, I thought that the edge speeds would be derived from the timestamps between my matched points and the edge lenght, but that doesn't seem to be the case. I then attempted to set speed limits in the car.lua file, but it had no effect. The maxspeed in the OSM network is empty.

My question is: How can I control the speed results to have it derived from my timestamp and edge length?

My objective is to extract the average speed by edge for each hour of the day.

Thank you.