Vehicular high-pressure hydrogen tanks are commonly required to install thermally-activated pressure relief device (TPRD) to prevent tank catastrophic rupture. However, the intended hydrogen release from TPRD may pose fire hazards to drivers, passengers and people outside the vehicle. This paper develops mitigation measures to reduce the risks of hydrogen fire introduced by TPRD. New rotatable design of the pressure relief device allows the system to actively adjust the hydrogen release direction towards void open space outside the vehicle to minimize the risks of hydrogen fires. To determine when and where to rotate, a monitoring system with infrared sensors, ultrasonic radar and temperature sensors, is designated to collect the indoor and outdoor information. A control strategy is also proposed to operate the safety system in an appropriate way. The cost-benefit analysis results show that the new mitigation can significantly reduce the risks of intended hydrogen releases from onboard pressure relief devices with total cost increasing by less than 1% of the vehicle's price, making it a cost-effective engineering solution. (C) 2020 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.