Slower speed when not using speed patterns layer?

[driesdesmet]

Hi again,

I'm using xRoute to calculate a route from

50.87596, 4.05801
to
50.87267, 4.01837

with the storedProfile set to "van".

I've calculated it in three ways:
1) With speed patterns enabled (Current time)
2) Without speed patterns enabled
3) With speed patterns enabled (optimistic)

From what I understand, optimistic always assumes that the vehicle can drive the maximum speed allowed for the road/type.

But for the 2nd call (without patterns) there's a 3 minute difference with the call that has patterns enabled. When looking at some segments, I see that their network class is 4 (with urban set to true), so I wouldn't expect a travel speed of 20km/h for a van.

Is there a certain default "pessimistic" estimate applied on routes without speed patterns, or am I missing something here?

[Joost]

Hello Dries,

About: "From what I understand, optimistic always assumes that the vehicle can drive the maximum speed allowed for the road/type."

This not exactly correct. Technically optimistic means that if has segments has multiple states depending on different time frames. xServer will use the state that gives the shortest drive time. So in the case of speed patterns it will still look at the speed pattern data to determine what the fast state is (usually somewhere around 1 in the morning) and base the driving time on this.

In the end this does come very close to "always drive the maximum speed" but there are here and there situation where this does not apply. For example think of a road with lots of traffic lights that are not synced.

As for calculating without speed patterns. Apart from network class we internally also classify the segment with a speed class. This combination will determine the theoretical driving speed that we use for determining the drive speed. For example have a look at Highways. On the average highway segment you can turn on cruise control at max allowed speed so they will receive a speed class to reflect this. However if you look at an intersection in the turns you have to reduce speed to make sure you can actually make the turn. Those "turn" segment will receive a speed class that reflects this and will result in a much lower driving speed. There are a lot of attributes that we use to determine the speed class.

Simplified I would say you can can compare routing without speed patterns as if you would route with speed patterns and use time consideration snapshot at 11:00 in the morning. It is by no means the exact explanation, but is the explanation that is simplest to understand while staying close in result to what actually is going on under the hood.

With Regards,
Joost