Starting Network Analysis > Common Analysis Parameters

Hierarchy Search Count

When searching the route, the searching will target the roads of higher level and neglect the roads of lower level. But in fact, even the roads of higher level are found, it is possible that the roads of lower level could reach the destination faster. However, to the hierarchy, once a road of higher level is found, it will search the roads of lower level no more. Thus, the possibility of finding the road of lower level that is faster than the road of higher level becomes 0. To avoid such situation, the latest version of Network Analyst provides with Hierarchy Search.

Now, we will illustrate the operation by setting the parameter of Hierarchy Search Count. If you set 1, it will search once forward the roads of higher level and search once backward the roads of lower level. After that, it continues to search based on the mode one way to the higher level and the other way to the lower level until one of them searches the route. If you set 3, when it searches the roads of higher level three times, it will search the roads of lower level once and so on. The default of Hierarchy Search is 0. If you set negative, it will search the roads of lower level as the priority to search the roads of higher level. For instance, if you set -2, it will search the roads of lower level twice and then search the higher level of road once. According to the frequency, the Hierarchy Search Count will search roads of higher level and lower level both to increase the chance to get the optimal route.

The simple Hierarchy Search setting is provided in Network Analyst. Users do not have to enter the exact parameter, but only need to choose to search the lower-level roads, which means to decrease the count of searching higher-level roads, or choose to search mainly the higher-level roads. Or you can simply search the higher-level roads by not using Hierarchy Search.

We can learn from the figures above that if the Hierarchy search is set “High”, the result picks the express way that drives longer distance to destination. If it is set “Low”, the result picks the local road that drives shorter distance. In conclusion, Hierarchy Search is not an absolute method, you need to decide according to the data you have or the need since choosing the higher-level road doesn't mean to get the shortest route and choosing the lower-level road doesn't mean to get the slowest route, either.