To address the challenges in the communication between infrastructure and vehicles in intelligent transportation systems, this paper applies the Intelligent Reflecting Surface (IRS) to the intelligent transportation system based on visible light transmission, and deeply analyzes its channel transmission model and the influence of road infrastructure parameters. By modeling the Non-Line-of-Sight (NLOS) channel between the infrastructure and vehicles,the transmission performance of signals in the NLOS channel is analyzed. The closed-form analytical solutions of the system performance are derived for the bit error rate, downtime probability, and block error rate of the IRS-assisted NLOS communication. The impact of the compound pointing error on the bit error rate, downtime probability, and block error rate of the IRS-assisted NLOS communication system is analyzed. The bit error rate performance under M-ary Phase Shift Key (MPSK) modulation and traditional key control modulation is also analyzed. The experimental results show that under the IRS-assisted NLOS transmission condition, when the link follows the double-Rayleigh distribution or the Rayleigh-Rice combined distribution, increasing the distance between the transceiver devices and the height of the street lamp will increase the bit error rate. Increasing the downtime threshold can increase the downtime probability. Increasing the number of transmitted bit blocks can improve the block error rate. MPSK modulation can reduce the system bit error rate more rapidly, and the performance is enhanced as the modulation order increases. After considering the pointing error to the system, its bit error rate, downtime probability and block error rate all increase. The proposed scheme can effectively enhance system communication performance.