Evaluating Sight Distances Dutch Ministry of Transport, Public Works and Water Management Civil Engineering Division Road Design Department Patrick Broeren Evaluating Sight Distances A Practical Tool for Highway Design
Contents presentation Introduction Sight Distances Application Zicht Case Study Further Developments Conclusion TRB
Introduction Driving behavior based on visual perception of a road For traffic flow and safety reasons, drivers need to see a minimum length of the road ahead Sight distance on a road should be sufficient to carry out a necessary maneuver before reaching a stionary object TRB
Sight distances Dutch design guidelines (ROA): Stopping sight distance (queues) Maneuver sight distance (small object) Road view sight distance (edge line marking) Passing sight distance (overtaking) Local sight distances (intersections, traffic signs) TRB
Sight distances International variation in sight distance calculations Important sight distance parameters: (design) speed eye height perception reaction time action time (braking, overtaking) deceleration rate (stopping sight) TRB
Sight distances Stopping sight distance, design speed = 120 km/h TRB
Sight distances Check visibility object in 3D road design TRB
Application Zicht Dutch Ministry of Transport and NedGraphics have developed a new software application for calculating sight distances Zicht (Dutch for “sight”) is suitable for: Practical use in complex road design Research on the effects of sight distance parameter variations TRB
Application Zicht Calculations based on visualization techniques Visibility object is checked with ray-trace module Module projects rays from observation point driver onto sight distance object (obstacle, taillight, marking) What do you need ? AutoCAD 2000 (Map, LDD, 2000i) 3D road and terrain model consisting of 3D-faces and polylines TRB
Ray-trace calculations TRB
Minimum sight distances Design speed Minimum sight distances Eye Height Calculation Accuracy TRB
Table TRB
Minimum sight distance Present sight distance Graph station TRB
Perspective views TRB
Case study Crossing of Highway A4 and High Speed Rail Link Amsterdam – Paris Alignement A4 checked on sight distances and drivers view with Zicht TRB
Present maneuver sight distances not sufficient First design: Present maneuver sight distances not sufficient Section of 100 m, sight distance deficit max. 45 m Second design: Alignment changed => design meets guidelines TRB
Further developments International, AASHTO-version of Zicht Extending the calculation model with passing sight distances More options for preparation of the road and terrain model Animation tool TRB
Conclusion With modern CAD-tools, road designers can check sight distances in 3D Higher quality of design Research purposes Information Zicht: www.sightlines.nl Demo: meet me after this session ! Questions, remarks, suggestions ???? TRB