As some of you might noticed, in the last months we’ve been focusing a lot of our attention & resources on our OSM initiatives. We’ve contributed in that way we though it will bring the highest value – building tools that would benefit the entire community.

One of our latest release was the “Traffic Flow Direction” tool, a new OSM tool based on Scout GPS probe data. We’ve presented it in a previous blog post, but we owe you a few more details on how easy it can be used and how you can make the most out of it.

So, here it is, “the missing manual” for the “Traffic Flow Directions”, explained by our colleague Martjin.

Let’s recap- why are we using it? To make it easy to find and correct OSM ways that we think are missing a oneway tag, based on billions of GPS points from Scout users.



*images courtesy of Martjin

The basic steps you need to follow:

1. Installation

This is a JOSM plugin so, installation works like any JOSM plugin.

  • Go to JOSM preferences.
  • Select the Plugins tab and look for the TrafficFlowDirection entry.
  • Select it and click ‘Update Plugins’ at the bottom. After JOSM completes installing the plugin, restart JOSM and you should see the main components of the plugin appear in the JOSM interface: the overlay on the map and the plugin panel.

2. Usage

The visual components of the Traffic Flow Direction are a map overlay and a settings / information panel. The map overlay shows clusters of suspected errors at low zoom levels, and individual errors at high zoom levels.

  • Zoom in on an area you want to work on and you will start seeing individual arrows. The arrows depict OSM ways that should have a oneway tag in the indicated direction, according to our GPS data.
  • Click on an arrow to select it and find out more in the Traffic Flow Direction panel:
  • Zoomed in to an area where you want to fix some direction errors, make sure you have the best possible aerial imagery layer for your area enabled.

Look for clues in the aerial image: the markings on the road (notice how the crossing street has a half stop line indicating that this is a two way street), check arrows and painted speed limits close to the intersections, check the direction of parked cars and use the local knowledge

  • Download the data for the area. Before you add oneway=yes though, check if it applies to the entire way. The OSM way may be longer than the segment we suggest. This has to do with the way we internally process OSM data. We split the ways at each intersection. You may need to split the way before you apply the oneway tag.

Other thing to watch out for is the directionality of the OSM way. If the direction of the way in OSM (the order of the nodes, basically) is the opposite of the oneway direction, you either need to tag the way with oneway=-1 or reverse the direction of the way first.

  • After you make the oneway improvements, upload the change set with trafficflowdirection in the source.
  • Mark the issue as Closed. Do this by first making the TrafficFlowDirection layer active and selecting the issue you just solved
  • Click the green lock in the plugin panel, add a comment, and close the issue.

If you find that after inspecting the aerial image or your local knowledge, the way is really not one-way, you can mark the issue as Invalid instead, using the red exclamation mark icon in the plugin panel.

3. Filtering

We define three confidence levels for the suspected Traffic Flow Direction errors (Check on the ‘filter’ icon in the tool panel). These levels are based on different thresholds for the total number of trips and the percentage going of trips going in one direction.


*images courtesy of Martjin

4. Commenting

You can comment on the selected issue by clicking the blue text bubble icon in the plugin panel.


*images courtesy of Martjin

If you want to use a different OSM editor you can use the Traffic Flow Direction Web tool. The tool is similar to the Missing Roads web tool. It will show a heatmap at lower zoom levels, and individual errors at higher zoom levels. It allows for filtering by status and confidence level.

Below is the colorful scene you get when you enable Missing Roads and Traffic Flow Direction at the same time:


*images courtesy of Martjin

Now let’s enjoy some mapping time! Happy mapping!