The way to Hanoi by backroads

This is the way to Hanoi by backroads (excluding large highways, and prioritizing small roads over big roads)

I am located in Thai Nguyen city, which is about 80 km North of the Hanoi. The way to get to Hanoi is usually by bus, which travels on the motorway (aka freeway). I wanted to know if I can go to Hanoi on a bicycle, taking the back roads. The goal of this project was to find the optimal route to take by bicycle, with the priority being smaller roads.

First, I created a road network which excludes the major highways.

I know that I don’t want to ride my bicycle on the major highways at all, so I don’t need to include them in my road network. I downloaded from OSM only the highways in the smallest 3 classes.

Second, I prioritized smaller roads over bigger roads.

I prefer smaller roads, even if it means going a slightly greater distance. I want the tool to find the route that takes the smallest roads as much as possible.

Unclassified roads → Most preferred

Tertiary roads → Second priority

Secondary roads → Least preferred

To do this, I basically tell it, ‘smaller roads are faster, bigger roads are slower’. Then I tell it, ‘go find the fastest route’, and so it finds the route with more small roads.

In the attribute table of the highway layer, I used the field calculator to create a new field called ‘speed’. I calculated it as follows:

CASE
  WHEN "highway" IN ('unclassified', 'unclassified_link') THEN 30
  WHEN "highway" IN ('tertiary', 'tertiary_link') THEN 20
  WHEN "highway" IN ('secondary', 'secondary_link') THEN 10
END

I then ran the Shortest Path tool in QGIS with the “Fastest Path” option and the new attribute selected for the “Speed Field”. Since the tool prioritizes higher speeds, roads with higher values in the new field are preferred. The resulting output is more Tertiary highway than anything else.