Civil Engineering DivisionRoad Design Department

Patrick Broeren

Evaluating Sight DistancesA Practical Tool for Highway Design

Dutch Ministry of Transport, Public Works and Water Management

TRB 2

Contents presentation

1. Introduction

2. Sight Distances

3. Application Zicht

4. Case Study

5. Further Developments

6. Conclusion

TRB 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

TRB 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)

TRB 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)

TRB 6

Sight distances

• Stopping sight distance, design speed = 120 km/h

0

50

100

150

200

250

300

Switzerland

Japan

Italy

Canada

Australia

US

Germany

Netherlands

UK

TRB 7

Sight distances

• Check visibility object in 3D road design

TRB 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

TRB 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

TRB 10

Ray-trace calculations

TRB 11

Design speed

Minimum sight distances

Eye Height

CalculationAccuracy

TRB 12

Table

TRB 13

Graphstation

Presentsight distance

Minimumsight distance

TRB 14

Perspective views

TRB 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

TRB 16

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 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

TRB 18

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 ????