In all suits against railroads for personal injury, property damage, or death caused by the running of trains in this state, contributory negligence shall not prevent a recovery where the negligence of the person so injured, damaged, or killed is of a lesser degree than the negligence of the officers, agents, servants, or employees of the railroad causing the injury, damage, or death complained of. However, where contributory negligence is shown on the part of the person injured, damaged, or killed, the amount of the recovery shall be diminished in proportion to the contributory negligence.