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Keypoint Annotation- Road Arrow Case Study

We often see various arrows on the road. These arrows are road traffic markers with a guiding function, indicating that the road ahead can only be driven according to the guiding arrows on the road surface.

They mainly provide guiding information to traffic participants. The indicator type generally gives pedestrians and drivers exact road traffic information to make the road traffic smooth and safe.

How do people usually drive?

  • Analysis: analyze whether to accelerate, decelerate, or stop based on experience
  • Make decisions: Act based on actual conditions, such as pressing the accelerator or brake.

The process of autonomous driving is no different from that of a human driver:

  • Analysis: real-time analysis of images through deep learning models to make decisions for the next step
  • Making decisions:

In order for driverless vehicles to be able to drive on the road safely and without obstacles, we need to allow vehicles to autonomously identify various types of road traffic markers. The scenarios for data annotation usually include lane changing and overtaking, passing intersections, unprotected left and right turns without traffic light control.

Let’s look at a key annotation case of road arrow.

Keypoint annotation

label the road arrows with key points. Each type of arrow has a fixed number of points. The points are labeled counterclockwise and connected in order.

1 Labeling types

Road arrows
















2 Labeling requirements

  • If it is not clear what type of arrow it is due to occlusion, or if part of it is hard to tell, don’t label the it
  • There shall be no missing or wrong labeling


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