Road Speed Design

Design speed is the maximum safe speed that can be maintained over a specified section of the roads or highways when conditions are so favorable that the design features of the highway govern. This design speed is depend the classification, urban and rural areas, terrain - including economic matters. All road's elements are depending to the this speed. Hence, the table are provided in accordance with the AASHTO.

As we can see the design speed a varies from place to place even it has the same category such as the Freeway - in rural design speed are 120 - 140kph in Rural, 100 - 120kph in Urban and in mountainous area 80 kph. The same as the Expressway, Arterial, Collector and Local. So this table is the best guide for Road Designer in selection of road design speed.

The ramps within a grade-separated interchanges typically have a lower design speed than that of a mainline. Table 8-7 should be used as the minimum design speed.