Road weighting

The functionality of road weighting has been altered through a patch application. If using a weighted roads data base please see a desription of patch.

In any region some transportation lines may have more affect upon urbanization than others. Through road weighting this type of influence may be incorporated into the model.

How road weighting works:
Road weighting does not affect a road pixel's likelihood of being found during a road search (see: equation 4.1 of road influenced growth, and road_gravity_coefficient). All road pixels have an equal probability to influence urban development. Instead, the weighting affects how the new urban center may be dispersed along the road network during the random walk (see: equation 4.2 of road influenced growth, and dispersion_coefficient). The highest road weight will allow a maximum distance, or number of steps, for the new urban center to travel along the road. A lower weight will cause some porportion of this maximum distance to be traveled. In this way smaller roads will have a more local affect, while larger roads may allow urbanization to occur further away along the network.

• Applied value is derived from the road pixel value by:

  run_value = (roads(i, j) / max_road_value * dispersion_coefficient)

  where run_value is the maximum number of steps traveled along the road network by an urban pixel. The value of a road pixel at a given location is described by road(i,j). Max_road_value is defined as 100. Run_value is at a maximum of 100 when (road(i,j) == max_road_value) and (dispersion_coefficient == 100).