1. Waymo's driverless cars have been exhibiting some unexpected behavior in Phoenix, Arizona, where the company has been testing its autonomous vehicles. The cars have been observed honking at each other throughout the night, seemingly without any apparent reason or purpose.

2. This unusual behavior has puzzled both Waymo and the local residents, who have reported being woken up by the constant honking from the driverless cars. Waymo has acknowledged the issue and stated that they are investigating the cause of this unexpected behavior.

3. The article suggests that this incident highlights the ongoing challenges and complexities involved in the development of fully autonomous vehicles. It also raises questions about the reliability and safety of these systems, particularly when they exhibit unpredictable behaviors in real-world scenarios.