Road and Motorway Design
Review of Design Rules relating to Visibility and Radii of Crest Curves in the Vertical Alignment
This guide revises the geometric design technical baselines with regard to visibility and crest curve radii in the vertical alignment:
• Firstly, it revises all visibility rules to reflect the current state of the art, taking a performance-oriented approach. This provides the basis for harmonising the rules contained in the various technical baselines;
• Secondly, it revises the design rules defining the minimum radii of crest curves in the vertical alignment.
For the French national road network, this document is considered to be an Instruction, as determined by the Technical Memorandum issued on 01/10/2018. For other road networks, authorities may use this guide, which is intended for use by all developers, when defining projects for which they are the project owner.
Part 1
Review of Visibility Rules
1 - Introduction
2 - General provisions
3 - Visibility of obstacles
4 - Visibility on bends
5 - Visibility at standard at-grade junctions
6 - Visibility at roundabouts
7 - Visibility at traffic light-controlled junctions
8 - Visibility of exits (at interchanges, rest and service areas)
9 - Visibility of entrances (at interchanges, rest and service areas)
10 - Visibility at slip roads and branches
11 - Visibility under structures
12 - Visibility of refuges
13 - Visibility of arrester beds
14 - Visibility of emergency accesses
15 - Overtaking visibility (on single-carriageway roads)
16 - Visibility for public transport lanes
17 - Visibility of pedestrian crossings
Review of Minimum Radii of Crest Curves in the Vertical Alignment
1 - Introduction
2 - Recommendations
Crest curve radii must be determined according to the visibility to be provided
(see Part 1 "Review of Visibility Guidelines").
Bibliography
Glossary
Table of notes
Appendix 1 - Principal Sight Distances
Appendix 2 - Summary of Visibility Rule Verification Conditions
Appendix 3 - Visibility Calculations
Appendix 4 - Use of the "Stopwatch Method" to Measure Visibility Conditions at At-Grade Junctions
Appendix 5 - Conventional Speed on Branches and Slip roads
