# Evaluation of Adjustment Effects of Highway Guide Signs Based on the TOPSIS Method
## 4 Construction of Evaluation Index System
### Evaluation Metric Determination
#### 4.3.2 Readability Indicators
\[D_{10}=1-g_{26}/G \tag{19}\]  
\(D_{10}\) represents the rate of signs positioned correctly, while \(g_{26}\) denotes the number of signs that are tilted among the directional signs. Effectiveness of information retrieval (D\({}_{11}\))  
The goal of guide signs is to provide timely and accurate information to road users. However, the effectiveness of information retrieval can be influenced by the design of signage and external factors. To assess user satisfaction with the ease of information retrieval, a five-level Likert scale is employed, with the following scores: very satisfied (5 points), satisfied (4 points), neutral (3 points), dissatisfied (2 points), very dissatisfied (1 point). Score = Total score/(5* sum of questionnaires). To address the factors influencing the continuity of guide signs, the following evaluation indicators are proposed. Reasonableness rate of hierarchical information selection (D\({}_{12}\))  
Information on guide signs should follow the hierarchical structure outlined in the standards, including both advance guide signs and confirmation signs at intersections. This indicator measures the proportion of signs with appropriately selected hierarchical information among all destination distance signs. It is defined as the ratio of signs with appropriately selected hierarchical information to the total number of distance signs. \[D_{12}=1-g_{31}/G_{2} \tag{20}\]  
\(D_{12}\) represents the rate of reasonable selection of information layers; \(g_{31}\) denotes the number of signs with unreasonable information layers; \(G_{2}\) is the total number of distance signs. Satisfaction with information selection (D\({}_{13}\))Given the complexity of highway operations and the varying levels of familiarity drivers have with road conditions, user needs and capacities to process guide sign information may differ based on individual cognitive abilities and physical conditions. Therefore, information selection should strive to meet the diverse needs of road users. To assess user satisfaction with the information provided, a five-level Likert scale is employed, with the following scores: very satisfied (5 points), satisfied (4 points), neutral (3 points), dissatisfied (2 points), very dissatisfied (1 point). Score = Total score/(5* sum of questionnaires). Continuity rate of guidance information (D14)  
This indicator assesses interruptions in guidance information along highways. Each interchange is treated as an evaluation unit, measuring the consistency of destination information through destination distance signs. Specifically, it checks the destination consistency from the first row of a distance sign to the advance guide and confirmation signs of the next exit. If the destination information changes before reaching the next exit, it is considered a break in continuity. This indicator is defined as the ratio of uninterrupted interchanges to the total number N.  
\[D_{14}=1-n_{2}/N \tag{21}\]  
\(D_{14}\) represents the continuity rate of guiding information; \(n_{2}\) denotes the number of interchanges with uninterrupted guidance information. Completeness rate of advance signs (D15)  
Advance guide signs must be installed along highways or urban expressways at 2 km, 1 km, 500 m, and at the beginning of the deceleration lane transition section. Each interchange serves as an evaluation unit. The completeness rate is defined as the ratio of interchanges with fully installed advance signs to the total number N of interchanges. \[D_{15}=1-n_{3}/N \tag{22}\]  
\(D_{15}\) represents the completeness rate of exit warning signs; \(n_{3}\) denotes the number of interchanges with incomplete exit warning signs. The factors influencing the consistency of guide signs primarily include the reasonableness of the advisory sign information, the accuracy of reaching destinations, and the effectiveness of path guidance. The following evaluation indicators are proposed to assess these factors.