1. 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

2. Contents presentation
Introduction
Sight Distances
Application Zicht
Case Study
Further Developments
Conclusion
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3. 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
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4. 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)
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5. 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)
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6. Sight distances
Stopping sight distance, design speed = 120 km/h
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7. Sight distances
Check visibility object in 3D road design
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8. 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
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9. 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
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10. Ray-trace calculations
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11. Minimum sight distances
Design speed
Minimum sight distances
Eye Height
Calculation
Accuracy
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12. Table
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13. Minimum
sight distance
Present
sight distance
Graph
station
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14. Perspective views
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15. Case study
Crossing of Highway A4 and High Speed Rail Link Amsterdam – Paris
Alignement A4 checked on sight distances and drivers view with Zicht
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16. 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
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17. 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
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18. Conclusion
With modern CAD-tools, road designers can check sight distances in 3D
Higher quality of design
Research purposes
Information Zicht:
Demo: meet me after this session !
Questions, remarks, suggestions ????
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