In order to eliminate the restriction of the return spring stiffness on the power generation and system reliability of the energy harvesting speed bump with the full wave mechanical rectifier, a dual-speed bump energy harvester (DBEH) based on the half-wave mechanical rectifier was proposed. The device utilized a mechanical transmission module to convert the downward linear movement of two speed bumps, driven by wheels, into the one-way rotary movement of a single generator shaft, thereby converting mechanical energy into electrical energy. The unidirectional motion conversion reduced the demand for the load of the return spring. The theoretical model of the wheel excitation and speed bump dynamics was established and verified by road tests. Based on the theoretical model, the power generation performance of DBEH was studied by numerical simulation. The research results indicate that the root mean square (RMS) power and output electrical energy of the system increase with the increase of external excitation amplitude and the decrease of the spring stiffness. When the load resistance value is 7-9 Ω, the output performance of the system is optimal. Compared to reducing the gear radius, increasing the speed of the gearbox has a more significant impact on the improvement of system output. A small inertia flywheel can effectively improve the system’s capture of the mechanical energy and the conversion rate from the mechanical energy to the electrical energy.