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Discrepancy in time-varying travel time data (Google MAP API) #3424

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luchengqi7 opened this issue Aug 22, 2024 · 1 comment
Open

Discrepancy in time-varying travel time data (Google MAP API) #3424

luchengqi7 opened this issue Aug 22, 2024 · 1 comment
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@luchengqi7
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I have tried to quest the travel time data for some OD pairs from the "SampleValidationRoutes" at different time of the day (01:00, 04:00, 07:00, 10:00, 13:00, 16:00, 19:00, 22:00). The pattern of the travel time differs from that I get from Google Map manually.

From the automated script, the daily curve looks like this:
time-varying-travel-time
The values are normalized to travel time at 1:00 and the line showed the average value of 19 randomly chosen OD pairs.

From the manual check on the Google Map, the daily curve looks like this:
image
Here I have manually recorded the travel time of 3 OD pairs at the same set of time stamps.

It can be seen that from the automated script, the minimum travel time happens at around 19:00, while the manual checks suggest the shortest travel time happen at 1:00 and 4:00.

Based on my personal experience, I would say the results returned by manual checks are more reasonable. Since the automated script is different from the previous script, it is a little bit challenging to read out the individual response from the API. So I can only make some guess. One likely reason is that Google API usually return 2 sets of routes: something like "base route" and "route". One is probably without congestion/traffic light/other aspects, while the other is a more realistic estimation. Maybe the base route is somehow read from the API.

@rakow
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rakow commented Aug 22, 2024

I believe the reason is that you query routes in a completly different time zone, hence the shift in the pattern. We will have to check how we can use local time in the api.

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