Autonomous Driving Systems (ADSs), which replace humans to drive vehicles, are complex software systems deployed in autonomous vehicles (AVs). Since the execution of ADSs highly relies on maps, it is essential to perform global map-based testing for ADSs to guarantee their correctness and AVs’ safety in different situations. Existing methods focus more on specific scenarios rather than global testing throughout the map. Testing on a global map is challenging since the complex lane connections in a map can generate enormous scenarios. In this work, we propose ATLAS, an approach to ADSs’ collision avoidance testing using map topology-based scenario classification. The key insight of ATLAS is to generate diverse testing scenarios by classifying junction lanes according to their topology-based interaction patterns. First, ATLAS divides the junction lanes in a map into different classes such that an ADS can execute similar collision avoidance maneuvers on the lanes in the same class. Second, for each class, ATLAS selects one junction lane to construct the testing scenario and generate test cases using genetic algorithm. Finally, we implement and evaluate ATLAS on Baidu Apollo with the LGSVL simulator on the San Francisco map. Results show that ATLAS exposes nine types of real issues in Apollo 6.0 and reduces the number of junction lanes for testing by 98%.