An unprecedented road test of a self-driving taxi using a fifth-generation, or 5G, ultrahigh-speed wireless network started in Tokyo on Thursday. Sompo Japan Insurance Inc., KDDI Corp., Tier IV Inc. and other firms tested the taxi on public roads around the metropolitan government office building in Shinjuku Ward. The companies hope to put such taxis into practical use in 2022 or later. A Toyota Motor Corp. JPN Taxi model equipped with software for autonomous driving developed by Tier IV, a startup based in Nagoya, is being used in the experimental project. The four-day test through Sunday is designed to check the safety, comfort and punctuality of the self-driving taxi in two modes -- one under complete remote monitoring and another under monitoring by a person sitting in the driver's seat.