Chapter 4.6.5 of the style manual shwos a table with road speeds and its
corresponding "highest speeds".
I created a small test map with roads of ca. 100 km length of all 5
road_types and added speed limits which translate into the 8 different
road_speed codes with the current (v3310) default style.
Following table shows my car navigation results on an Oregon 600 with
current firmware (3.90):
Roadspeed Distance Time Speed Simulationspeed
7 99,9 00:53:27 112,14 254
6 99,7 00:56:41 105,53 130
5 100 01:00 100,00 100
4 99,5 01:16 78,55 90
3 100 01:34 63,83 70
2 99,9 02:03 48,73 50
1 99,6 03:06 32,13 30
0 100 06:09 16,26 16
The "Speed" is calculated by dividing the distance to destination by the
time to destination;
the "Simulationspeed" is the speed shown on the device when you select
the simulation option.
The speeds do not depend on the road_type value.
The speeds for classes 0, 1, 2, 3, and 7 are multiples of 10mph.
When using a different routing type (e.g. pedestrian), the simulation
speed did not change (i.e. a pedestrian "walking" at 50 km/h...), but
the calculated time to destination changed (i.e. a pedestrian was doing
ca 5 km/h, a cyclist ca. 25 km/h).
With an Oregon 400 with old firmware (4.20), values are slightly different:
Roadspeed Distance Time Speed Simulationspeed
7 99,9 00:45:20 132,22 129
6 99,7 00:51:51 115,37 113
5 100 00:56 105,63 103
4 99,5 01:07 89,10 87
3 100 01:32 65,22 64
2 99,9 02:03 48,73 48
1 99,5 03:06 32,10 32
0 100 10:16 9,74 9
The main difference is in faster speed for higher road_speed types, but
lower simulation speed.
This means that Garmin uses different speeds for calculating the time to
destination between different device types!
I hope this information helps the creators of maps, and helps to clarify
questions on why this route was taken instead of that...
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