PURPOSES: In this paper, the effectiveness of speed-maintained standardization in road geometry on environmental impact at a downward slope location, based on greenhouse gas (GHG) emission indicators, was studied. Specifically, the aim of this study was to ascertain whether speed-maintained standardization resulted in decreased CO2 emissions as well as noise pollution, due to reduced vehicle speeds. METHODS : In this study, speed-maintained standardization in road geometry was proposed as a means to reduce vehicle speeds, with a view to reducing CO2 emissions and noise pollution. This technique was applied at a downward slope location. The vehicle speeds, CO2 emissions, and noise levels before and after application of speed-maintained standardization were compared. RESULTS: It was found that speed-maintained standardization was effective as a means to reduce speed, as well as CO2 emissions and noise pollution. By applying speed-maintained standardization, it was confirmed that vehicle speeds were reduced consistently. As a result, CO2 emissions and noise levels were decreased by 9% and 11%, respectively. CONCLUSIONS : This study confirmed that speed-maintained standardization in road geometry is effective in reducing vehicle speeds, CO2 emissions, and noise levels. Moreover, there is further scope for the application of this method in the design of roads in urban and rural areas, as well as in the design of highways.

PURPOSES : This study aims to suggest the optimal spacing between speed humps which is placed at traffic calming areas including pedestrian priority zones, school zones, and residential areas. METHODS: The study measured the operating speed of vehicles passing through two successive humps by using laser gun in 0.2 seconds interval, and analysed the basic statistical characteristics of speeds data to have an insight on the relationship between spacing and speed. Assumption was made to derive the maximum spacing within which two successive humps influence each other. RESULTS: The statistically significant model explaining the relationship between spacing and 85th percentile speed of vehicles was derived as well as the maximum spacing maintained in order to take the benefits of successive installation of humps. CONCLUSIONS: Spacing of 20 meters was suggested to achieve the widely accepted target speed of 30 km/h in traffic calming zone, and spacing of 70 meters was suggested as a maximum spacing. The comparison across the studies were made and empirical reasoning the difference of results between studies was discussed as well as the future studies.

PURPOSES : The lack of details of guidelines on how to install the Chicane for traffic calming leads the practical difference across the calming areas, so the benefits expected from these facilities are not hardly observed. In this context, this study analysed the relationship between the geometric design alternatives of Chicane with the dynamic behaviour of vehicles in terms of speed and trajectory. METHODS : The study analysed vehicle dynamic behaviour using dynamic analysis program Auto-Turn under various geometric conditions of Chicane. RESULTS : This study suggested the design alternatives of Chicane using terms such as "longitudinal displacement value", "lateral displacement value", etc. which are defined in the study. The suggested combination set is fulfilling the desired or target speed of vehicles and clearance between vehicle and roadside at the same time. CONCLUSIONS : The results from this study can be applied to install Chicane corresponding to the local condition where target speed is 30km/h. The study showed the design alternatives of chicane corresponding to the given road cross-sectional design and clearance to roadside for passenger cars and light truck respectively.