In order to study the causes of traffic accidents caused by small and oversized cars on multi-lane ramps, an on-ramp lane number selection model based on line-of-sight analysis was established, and the model was applied to the on-ramp lane number test of actual interchanges. First of all, the stopping sight distance index on the ramp car overtaking process is analyzed, and the selection model of the ramp lane number to meet the sight distance requirement is established. Then, the 3 key elements of the ramp circle radius, the circular curve length, the circular curve and the transition curve combination are thoroughly studied, and the recommended values of the number of ramp lanes satisfying the sight distance requirement are put forward. The interchange of observation bridge and interchange of middle tunnel expressway is inspected. The results show that on multi-lane ramps with small radius, the linear combination of short circular curve + long transition curve and the ratio of radius of circular curve to parameters of transition curve is 1:2 can better meet the requirements of visual distance. When the design speed of multi-lane ramp is 30 km/h, the radius of circular curve of multi-lane ramp should be greater than 41 M. If the limit radius is adopted, the length of circular curve should not be greater than 10 m. When the design speed is 80 km/h, the radius of circular curve of multi-lane ramp should be greater than 560 M. If the limit radius is adopted, the length of circular curve should not be greater than 30 m.

CICTP