A traffic flow map is a visualisation of the traffic flow levels on the road segments in a road network and is fundamental for transport planning. Whilst traffic flow maps are a rich source of information about vehicle mobility patterns, they are also costly in terms of time and resources to compute for any reasonably sized road network. To alleviate this cost burden, we use empirical GNSS (Global Navigation Satellite Systems) trajectory data (which include the well-known GPS) as our input data source since they can be acquired with low marginal cost whilst offering extensive spatio-temporal coverage.

In the image comparison, we zoom into 391 trajectories collected in Hannover, Germany. The green circles of the vehicle trajectories can deviate from the road network. If we move the slider from right to left, the error-prone empirical trajectories are replaced with our innovative flow map with unambiguous traffic flows on each road segment.

Details of this innovation based on aligning road segments to the most locally representative segment are in the article Using iterated local alignment to aggregate trajectory data into a traffic flow map, published in the Journal of Location Based Services. Any questions about the methodology can be addressed to Tarn Duong.