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...