An application of direct method and ball-bank indicator method to determine advisory speeds for horizontal curves in Vietnam

  • Do Duy Dinh Faculty of Bridge and Roads, National University of Civil Engineering, 55 Giai Phong road, Hai Ba Trung district, Hanoi, Vietnam
  • Le Tien Dung T&D Designer Consultants and Construction, Hanoi, Vietnam


Advisory speed signs on horizontal curves have been widely used in many countries over the world to improve traffic safety; however these road signs have not been applied in Vietnam. This paper aims to use the direct method and ball-bank indicator one to determine advisory speeds for 10 horizontal curves all with speed limit of 60 km/h on National Highway No. 4A in Lang Son province. The results showed that, advisory speeds were determined by the ball-bank indicator method ranging from 40 to 45 km/h for curves with radius of 70 m or less and from 50 to 55 km/h for curves with radius varying from 75 m to 120 m. As compared to the ball bank indicator method, advisory speeds determined by the direct method were 0 – 5 km/h higher if using 85th percentile speeds of cars, but 5 – 10 km/h lower if using average speeds of trucks.


advisory speed limit; operating speed; horizontal curve; ball-bank indicator; traffic safety.


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How to Cite
Dinh, D. D., and L. T. Dung. “An Application of Direct Method and Ball-Bank Indicator Method to Determine Advisory Speeds for Horizontal Curves in Vietnam”. Journal of Science and Technology in Civil Engineering (STCE) - NUCE, Vol. 14, no. 1, Jan. 2020, pp. 136-45, doi:10.31814/stce.nuce2020-14(1)-12.
Research Papers