The Effect of Turn Signal Onset on Lateral Performance Measures When Overtaking a Lead Vehicle - Using Naturalistic Driving Environment

Abstract

Lane changes occur very frequently on freeways. For the development of automated vehicles (AV), the detection of the other vehicles’ lane change maneuvers is an important task. Practically, turn signal is the most direct indicator to show the driver’s intention to change lanes. This study explored the Safety Pilot field-operational-test (SPFOT) database to investigate the use of turn signal and the relationship between the turn signal onset time and lane change performance measures, in order to assist AV anticipating other road users’ maneuvers. Driving data from 130 instrumented vehicles were extracted and 31,211 overtaking events were selected. It was found that the turn signal was used for about 70% of lane changes, and during half of those the turn signal was activated after the initiation of the lane change maneuver. Results showed that leftward overtaking maneuvers had longer lane change duration with slower lateral speed and lateral acceleration than rightward ones when the turn signal was not used. It was further found that the lane change duration can be estimated by the turn signal onset time. The shortest lane change durations of 5.33 s and 4.66 s occurred during those maneuvers when the turn signal was activated at 4.5 s and 5 s before the start of the leftward and rightward lane changes, respectively.