The low luminance and the monotony of highway tunnels are likely to cause drivers to experience a visual illusion while driving. Drivers tend to underestimate their speed and thus are exposed to a higher risk of relatively severe traffic accidents. Finding a low-cost way to reduce this visual illusion and to improve traffic safety is a challenge for current highway tunnel operations. High-frequency visual information can make a driver overestimate speed; low-frequency visual information may induce a driver to underestimate speed. However, quantitative investigations of the influence of visual information of various frequencies and luminance levels on drivers' speed perception are lacking. This paper describes a driving simulation model created with Autodesk's 3ds Max modeling software and tests carried out with simulators and E-Prime research software. The mechanisms of speed perception and reaction time were studied to consider the effect of visual information with high frequencies and with combined high and low frequencies under different luminance levels (100%, 50%, and 25% of standard luminance). The test results revealed that speed overestimation was caused mainly by high-frequency visual information. This overestimation could be reduced by combining high-frequency visual information with low-frequency visual information. With higher luminance, speed overestimation was lessened and drivers' reaction time was shorter. It is suggested that visual information with combined frequencies be employed to control drivers' illusions of speed and to enhance traffic safety.

As typical weak visual reference systems, highway tunnels have low illumination, monotonous environment and few references, which may cause severe visual illusion and reduce drivers’ speed perception ability. Thus, drivers tend to underestimate their driving speed, which may induce speeding behaviours that result in rear-end collisions. The cost-effective pavement markings installed on both sides of the lane or shoulder may make drivers overestimate their speed. This perception can help ensure safe driving and regulate driving behaviour effectively. This study analyses the effects of sidewall markings in typical low luminance highway tunnels, specifically observing how their angles and lengths affect the driver’s speed perception. A three-dimensional model of highway tunnels was built in a driving simulator. Psychophysical tests of speed perception were carried out by the method of limits. The simulation tests studied the Stimulus of Subjectively Equal Speed (SSES) and reaction time in relation to sidewall markings with different angles. Furthermore, based on the optimal angle, the effects of sidewall marking with different lengths on speed perception were also analysed. The test results reveal that the angle and length of sidewall markings have a significant impact on the driver’s SSES and reaction time. Moreover, the level of speed overestimation decreases with the increase of angle or length of sidewall marking. As the angle of sidewall marking gradually increases, the maximum reaction time first increases and then decreases. Within the angle of sidewall marking of 15°, the subjects have the highest speed overestimation and an easy speed judgment. This may due to Zöllner illusion, the driver’s perception of lane width shrinks may induce deceleration behaviour.