Abstract
In the present decade along the increasing trend of using private vehicles, calming the local streets and residential areas has been important for local authorities. There are many unsuccessful experiences of traffic calming implementations because of lacking knowledge and engineered assessment before implementing them. Considering the design speed of traffic, calming measure is an essential factor to employ these measures. Design speed of different size of speed humps is investigated in previous studies because of its circular shape but for speed tables it is unknown. In this research the design speeds of two common speed tables in the city of Tehran have been examined, 6.5 and 8.5 m speed table. For calculating the design speed of the speed tables, we asked 220 drivers to participate in our experiment by installing a GPS tracker in their vehicles and encouraging them to drive normally. Crossing speeds over 6.5 and 8.5 m speed tables have been analyzed by collecting totally 220 samples. We pick out 100 correct samples for each speed table and the 85 th percentile speed has been calculated for them, consequently the results of 85 th percentile calculation of the crossing speeds have been proposed as the design speeds. For 6.5 m speed table, design speed is calculated 41.5 km/h and for 8.5 m speed table, design speed is calculated 47.5 km/h. the comparison of recent findings and past finding of 9.5 m speed table which is used in Denmark with a design speed of 80 km/h reveals that 1 m increasing with the length of a 6.5 speed table plateau will result 3 km/h increase in its design speed. The findings of this research can help traffic calming experts to take in consideration of the relation between speed table physical characteristics and its design speed. Furthermore by finding the design speed of speed tables, we can choose suitable speed tables for streets with different speed limits according to the design speed of speed tables.
Highlights
Vertical traffic calming measures are a group of physical measures including speed bump, speed hump and speed tables that their role is to slow down traffic speed and discourage through traffic or shortcut traffic to enter local areas
The place of implementing of traffic calming measure is important, for example regarding to design speed of speed bumps, they can be implemented in the parking lot, shopping mall, pedestrian zone and the places where the pedestrian movement is high and the speed limit adjusted to its lowest amount respectively, speed humps and speed tables are suitable for local street and collector streets (Ewing, 1999)
After collecting the crossing speeds for the speed tables from the GPS tracker, 85th percentile speed for each speed table is calculated through Eq (1)
Summary
Vertical traffic calming measures are a group of physical measures including speed bump, speed hump and speed tables that their role is to slow down traffic speed and discourage through traffic or shortcut traffic to enter local areas. Speed table is a flat topped speed hump which is more common in local collectors, which has great impact on traffic safety condition. The place of implementing of traffic calming measure is important, for example regarding to design speed of speed bumps, they can be implemented in the parking lot, shopping mall, pedestrian zone and the places where the pedestrian movement is high and the speed limit adjusted to its lowest amount respectively, speed humps and speed tables are suitable for local street and collector streets (Ewing, 1999)
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