| The contradiction between supply and demand of transportation system is increasingly apparent due to the continuous development of Chinese economy.It promotes new technologies to improve the operation of transportation system,especially with the information technology playing an important role in updating of ITS and improving of traffic operation efficiency.As an important traffic information releasing equipment of ITS,VMS is widely used in the management of urban roads and highways.It’s able to provide dynamic information for drivers and of great significance in evacuating traffic flow,avoiding congestion diffusing and balancing traffic volume.However,previous investigation discovers that the layout of VMS wasn’t competent,which means drivers have less utilization and trust of VMS information.The reason for this is the lacking of design standards in China such as the number and size of VMS,which influences driver’s ability to cognize VMS and makes VMS inefficient.Aiming at the problems existing in VMS involving driver’s cognition process and its design and layout,this paper focuses on the following four questions.VMS information quantification method:Information theory served as the foundation in classifying the commonly used traffic sign elements and respectively clarifying the calculation principles of information quantization of univocal element and combinatorial element.Considering the cognitive theory,the author defined the basic unit of information quantification and the amount of unit element information,and then built VMS information quantization model.Evaluation of driver’s information recognition:Based on the characteristics of driver’s visual perception,the author introduced the concept of recognition.Considering the main factors that respectively influences the valid recognition of static VMSs and dynamic VMSs,the author selected the suitable index to evaluate the degree of a driver effectively acquiring information from VMS.Finally,after using a recognition evaluation model and an actual experiment to evaluate VMSs,the results are as follows.When exceeding 90 bits,the amount of VMS is slightly overloaded.When the static VMS recognition rate is less than 0.8 or dynamic VMS cycle availability is less than 0.9,drivers cannot receive VMS information completely.Evaluation of driver’s information utilization:VMS is usually placed in front of the key point of traffic,and after getting information the driver need to keep useful information until arriving the key point for correct response.The author introduced the concept of the degree of information preservation based on the driver’s information processing process and experimental analysis of driver’s information acquisition under dynamic visual recognition condition.Summarizing the law of driver forgetting short-term memory,the author built a model for calculating the maximum short-term memory time of driver with different degree of information preservation.Check experiment using memory validity as evaluation index showed when the memory validity is between 0.85 and 1.5,VMS has better utilization.Analysis of driver’s cognitive load:To study the visual working memory load of driver caused by different information density of traffic signs in cognitive process,the E-Prime software was involved to obtain the response time and accuracy of experimental participants.Using the SPPS software to analyze experimental data,the results showed when the stimulus intensity is less than 14.16bit/m~2or the interval time of stimulus locates in 15s,the driver will bear proper workload.The author applied above conclusions to give suggested space over the combination layout of VMS and traditional static signs under different speed limit. |
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