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Examples of travel speed values while walking or driving on a flat surface are presented in the following two tables.
Land cover type | Speed (km/h) |
Urban and built-up area | 5 |
Low dense vegetation | 4 |
Medium dense vegetation | 3 |
Dense vegetation | 2 |
Bare soil | 5 |
Example of travel speed estimation on a flat surface per land cover type for walking scenario
Roads type | Speed (km/h) |
Motorway or Highway | 100 |
Dual lane roads | 80 |
Track, trails or footpaths | 20 |
Example of maximum travel speed for different types of roads (extracted from Toxopeus (1996) and Nelson (2000))
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In AccessMod, the scenario table allows for the attribution of a traveling mode (walking, motorized, and bicycling) and speed to each of the classes, and therefore each cell in which movement is allowed, contained in the merged land cover distribution grid (see Section 5.5.2).
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- class: Merged land cover class
- label: Merged land cover label
- speed: Travel speed (in km/h) on flat surfaces. The value must be greater or equal to zero (see below for the latter)
- mode: transportation mode considered for the given land cover class to be chosen from the following list:
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- MOTORIZED: the mode being applied to motorized vehicles when no corrections are being applied on the travelling speed, even if a DEM is used in the analysis.
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- WALKING: the mode applied when the population walks. In this case, a slope-based correction is applied to the indicated speed. This correction is based on Tobler’s formula (Tobler, 1993), which basically decreases or increase the effective walking speed depending on the steepness of the slope and this for up or down movements.
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- BICYCLING: a slope-based correction is applied to the indicated speed. See below for details.
class | label | speed | mode |
1 | Cropland | 3.0 | WALKING |
2 | Bare soil | 5.0 | WALKING |
4 | Dense forest | 3.0 | WALKING |
6 | Pasture | 4.0 | WALKING |
1016 | Highway | 120.0 | MOTORIZED |
1017 | National road | 80.0 | MOTORIZED |
1018 | Secondary road | 40.0 | MOTORIZED |
1019 | Residential road | 30.0 | MOTORIZED |
Example of a travelling scenario excel file
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- Weight of the cyclist : 80 kg
- Weight of the bicycle : 15 kg
- Rolling resistance coefficient : 0.012
- Frontal area : 0.445 m2
- Wind velocity : 0 km/h
- Temperature : 20°C
- Elevation : 500m
- Transmission resistance coefficient : 0.9
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A simplified description of the formula used can read as follows:
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- velocity = velocity of the cyclist on a flat surface
- velocityTotal = velocity of the wind + velocity
- resistanceBike = Resistance of the tires and the gravity
- resistanceAir = Frontal area * air density
- efficiencyTransmission = Transmission resistance coefficient
- power = power necessary to have the bike move at the given velocity on flat surface
The final velocity (Velocity, below) is estimated by resolving a non-linear equation with the Newton's method. The non-linear equation is defined with the following:
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F' = resistanceAir * (3.0* Velocity + Wind velocity) * Tv + resistanceBike
For the Newton technique, we used a maximum tolerance of 0.05 and maximum 10 iterations. If there is no convergence, the result is set to 0.0 kmh. A graphical example of the corrected speeds in function of the slope for that particular speed is shown in
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