Thermal comfort is an important subject to evaluate the quality of outdoor environments. This study investigated outdoor thermal conditions and the thermal comfort perception of pedestrians using walkways within a university campus in Thailand, located in the hot and humid tropical region. In this field study, microclimate measurements were conducted to assess the physiological equivalent temperature (PET) of walkways, and on-site questionnaire surveys (n = 400) were used to evaluate the thermal sensation votes of pedestrians in different walkway conditions. The results revealed that the neutral PET was 25.2 °C and its acceptable range was 24.6–32.0 °C. Most pedestrians accept the thermal conditions of all walkway types but at different levels of acceptability, albeit in a slightly warm sensation. Among different walkway types, the cantilever-covered walkway with sparse trees yields the closest PET to the neutral PET. The most comfortable and favorable walkway is that with a lower air temperature, less sunlight, and higher wind ventilation. The studies on the outdoor thermal comfort of pedestrian walkways could benefit urban planners and engineers in designing physical and environmental conditions of walkways as well as promoting non-motorized transport and green university campuses.

This study developed and evaluated free flow speed (FFS) estimation models for multilane highways in Thailand by applying multivariable linear regression. Data from 272 highway segments were analyzed considering the percentage of heavy vehicles, left shoulder width, and access point density. Highways were categorized into four-lanes and more-than-four-lanes configurations and further analyzed under different base free flow speeds (BFFS) ranging from 90 to 120 km/h. For four-lane highways, Model 1-2 (BFFS = 100 km/h) achieved the best predictive performance, with an R² of 0.9583, root mean squared error (RMSE) of 1.51, and mean absolute error (MAE) of 1.24. For more-than-four-lanes highways, Model 2-3 (BFFS = 110 km/h) performed best (R² = 0.9387, RMSE = 1.86, MAE = 1.46). All variables showed significant negative effects on FFS. The developed models provide practical tools for assessing roadway performance, thereby regulating speeds, and guiding infrastructure planning, enhancing safety and efficiency on Thai multilane highways.

This study develops a framework for evaluating the social and economic impacts of low-cost road safety improvement projects. The proposed framework applies the Social Return on Investment (SROI) approach to compare the socio-economic outcomes of road safety engineering interventions within 4 levels—Tier 1: removing severe conflicts, Tier 2: reducing speed, Tier 3: managing conflicts, and Tier 4: increasing awareness. Traditional evaluation methods focus on crash reduction and economic efficiency; however, they provide limited information on social outcomes and lack a systematic approach for comparing local road safety interventions. To address this gap, data from 15 road safety improvement projects at different study locations are used to assess the social and economic impacts for three stakeholder groups: road users, communities, and government agencies. The social outcome is converted into monetary values over a five-year evaluation period. Statistical and sensitivity analyses are applied to compare differences across the hierarchy of road safety interventions and evaluate the robustness of the SROI results. Results show that higher-level interventions generate the greater social returns. The average SROI ratios for Tiers 1 to 4 are 17.0, 15.6, 11.5, and 8.1, respectively. Statistical analysis shows a significant difference between intervention levels (F(3,11) = 16.51, p < 0.001). Crash reduction and community satisfaction were the main positive impacts, while increased travel time, fuel consumption, and emissions reduced SROI. The proposed framework provides practical guidance for evaluating low-cost road safety measures based on socio-economic performance in decision-making.