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Table 1 Summary of observed vehicle behaviours, possible reasons, applied solutions and occurrences

From: Digibus©: results from the first self-driving shuttle trial on a public road in Austria

Observed behaviour

Possible reason

Applied solution


Shuttle stopped for obstacle

• Parking vehicles on the roadside or at bus stops

• Bypassing the obstacle manually

• Setting the shuttle to automatic mode after the obstacle

• Frequent

Shuttle stopped for no apparent reason

• Branches of trees or shrubs on the roadside

• Wrongly detected obstacle

• Unreliable positioning

• Sensor reflections due to water lacquers, heavy rain or snowfall

• Setting the shuttle to automatic mode again for continuing the test drive

• If this was not successful, driving back manually to a safe parking position (e.g. bus stop)

• Frequent

Detection of other road users failed

• Velocities > 30 km/h of approaching or passing vehicles at left turns or exits from bus stops or side roads

• Dead angles of 360° LIDAR sensors due to vehicle’s own shading

• Low spatial resolution of the Velodyne VLP-16 LIDAR sensors

• Stopping the shuttle and taking over manual control

• Frequent

Unclear interaction with other road users

• Planned safety stops

• Stopping without any reason

• Is overtaking safe?

• Abandoned priority

• Missing trust by other road users

• Variable messages on the back screen of the vehicle

• Using hand signs if possible

• Frequent

Shuttle could not be set to automatic mode after a stop

• Vehicle being out of driving path

• Software problem

• Driving manually to the next safe parking position (e.g. bus stop)

• Applying one or several restarts

• Contacting the Navya supervision team for solving the problem via remote control

• Several test drives