The need to reduce energy consumption and electricity expense is the primary driving force behind generating renewable energy for the operation and maintenance of road tunnels. Existing kinetic energy harvesting solutions, such as piezoelectric or mechanical energy harvesting systems, failed to meet the relatively high power demand of road tunnels. Traditional piezoelectric methods only supply micro-electromechanical systems. Their low voltage leads piezoelectric methods to not be applicable in realistic facilities. Due to the transmission loss of energy in a mechanical motion rectifier, mechanical schemes also fail to promote the practical application of renewable kinetic energy harvesting. In this paper, we present a novel high-voltage kinetic energy harvesting system that is installed at the entrance and exit of a road tunnel. It harvests power wasted by vehicles passing over the harvester. The proposed system consists of four main steps: a speed bump and suspension, generator and power storage modules. Acting as the energy input, the speed bump module harvests kinetic energy created by running vehicles. The suspension module resets the speed bump by driving it upwards after vehicles depart from it. Meanwhile, the generator module generates electricity from the kinetic energy collected by the speed bump module. The power storage module rectifies the current and then stores the electrical energy in batteries. The high voltage obtained in the simulation and field tests is a proof that the retrofit mechanism of the energy harvesting system is beneficial and practical in generating energy for use in renewable road tunnels.