Road Surface Laws

This document describes the data you can use to create length/width, angle, curve and shoulder superelevation/widening laws for civil engineering objects. The administrator can edit an xml file, shared by the project team in the Data Setup.

This page discusses:

Road Specifications for Horizontal Alignment

Road specifications can be defined by Data Setup Resources. Traveled way right and left widths can be driven by dedicated length laws.

Modelling Overview

Vehicles and lanes defined in Data Setup are created in the 3D Shapes containing alignments. Vehicles have one and only one IfcPset_VehicleCommon. Lanes have only one IfcPset_LaneCommon.

The horizontal alignment is used to store the road specifications.

The horizontal point is used to store the road stretch specifications.

The road surface is used to store the angle and width laws.

Road Specifications Defined with the IfcPset_RoadCommon Extensions

The IfcPset_RoadCommon extensions are attached to the existing RoadType PLM objects.

Attribute Name Type Value/Description
Traveled way type Enumeration

Planar or Crowned

The attributes cannot be changed along the alignment. For instance, you cannot start a road as planar and end it as crowned.
Rotation mode Enumeration

Center line, Inner/Outer edge, Right, Left

The attributes cannot be changed along the alignment. For instance, you cannot start a road as planar and end it as crowned.
Design Vehicle String

The attribute ‘Symbol’ of IfcPset_VehicleCommon

The attributes cannot be changed along the alignment. For instance, you cannot start a road as planar and end it as crowned.
Design speed Speed -
Category String -
Normal slope Angle Way transversal slope in tangent
Right shoulder slope Angle Shoulder transversal slope in tangent
Left shoulder slope Angle Shoulder transversal slope in tangent
Widening transition Length

Length of the transition to go from the old width to the new one.

It applies to the traveled way widening only, not to the curve widening. For curve widening, the transition occurs over the superelevation runoff length.

Negative values are accepted; in that case, the transition occurs upstream.
Widening smoothing Length

Projected length of parabolas that smooth the widening.

“0” means the widening is applied linearly over the transition.

It applies to the traveled way widening only, not to the curve widening.
Roll over Angle

The attributes cannot be changed along the alignment. For instance, you cannot start a road as planar and end it as crowned.

Road Specifications Defined with the IfcPset_TraveledWayLaneDistribution Extensions

Attribute Name Type Value/Description
First way center {Lane;Direction} Pair of lane and direction. Direction is equal to 1 when traveling from alignment Start to alignment End. It is equal to -1 for the opposite way. 0 otherwise.
First way right side List of {Lane;Direction}

Pair of lane and direction. Direction is equal to 1 when traveling from alignment Start to alignment End. It is equal to -1 for the opposite way. 0 otherwise.

List order is important: it starts from the alignment towards the outside.
First way left side List of {Lane;Direction}

Pair of lane and direction. Direction is equal to 1 when traveling from alignment Start to alignment End. It is equal to -1 for the opposite way. 0 otherwise.

List order is important: it starts from the alignment towards the outside.

Road Specifications defined with the IfcPset_ShoulderLaneDistribution Extensions

Attribute Name Type Value/Description
First way right side List of {Lane;Direction} Pair of lane and direction. Direction is equal to 1 when traveling from alignment Start to alignment End. It is equal to -1 for the opposite way.
First way left side List of {Lane;Direction} Pair of lane and direction. Direction is equal to 1 when traveling from alignment Start to alignment End. It is equal to -1 for the opposite way.

Road Stretch specifications for Horizontal Alignment

Road Strech specifications are modeled by three lists of properties stored in an xml file that can be shared with the project team using Data Setup.

IfcPset_TraveledWayLaneDistribution and IfcPset_ShoulderLaneDistribution can be used to complete road stretch specifications.

Table 1. Road Specifications Defined with the IfcPset_RoadStretchCommon Extensions:
Attribute Name Type Value/Description
Deign speed Speed -
Category String -
Normal slope Angle Way transversal slope in tangent.
Right shoulder slope Angle Shoulder transversal slope in tangent.
Right shoulder slope Angle Shoulder transversal slope in tangent.
Widening transition Length

Length of the transition to go from the old width to the new one.

It applies to the traveled way widening only, not to the curve widening.

Negative values are accepted; in that case, the transition occurs upstream.
Widening smoothing Length

Projected length of parabolas that smooth the widening.

“0” means the widening is applied linearly over the transition.

It applies to the traveled way widening only, not to the curve widening.

General Widening

Default road specifications are now specified at the alignment level.

Crowned Road Specifications Defined with the IfcPset_RoadCommon Extensions

Attribute Name Type
Traveled way type Crowned
Rotation mode Center line
Design vehicle SU-9
Category -
Normal slope 2%
Widening transition 10m
Widening smoothing 2m
Roll-Over 8%

Traveled Way Distribution

Attribute Name Value
First way center {“Raised median”; 0}
First way right side {“3.5m lane – OneWay”; 1}
First way left side {“3.5m lane – OneWay”; -1}

Shoulder Distribution

Attribute Name Value
First way right side {“Emergency stop strip”; 0}
First way left side {“Emergency stop strip”; 0}

“SU-9” specifications

The following definition requires the availability of a vehicle and three lane types in the 3D Shape.

Attribute Name Value
Type Single-Unit Truck
Symbol SU-9
Height 3800m
Width 2440m
Length 9140m
Front overhang 1220m
Rear overhang 1830m
Wheelbase 6100m
Articulation wheelbases -
Empty speed limit 110km/h
Load speed limit 90km/h
Unloaded weight 2000kg
Payload 1500kg
Autonomous FALSE

“Raised median” specifications

Attribute Name Value
Name Raised median
Design vehicles -
Width 300m
Lateral clearance 0mm
Traveling direction None
Speed 0km/h

“3.5m lane - OneWay” specifications

Attribute Name Value
Name 3.5m lane - OneWay
Design vehicles SU-9
Width 3500m
Lateral clearance 600mm
Traveling direction Oneway
Speed 80km/h

“Emergency stop strip” specifications

Attribute Name Value
Name Emergency stop strip
Design vehicles SU-9
Width 2000m
Lateral clearance 300mm
Traveling direction None
Speed 0
Traveling direction Oneway
Speed 80km/h

“Turnout” specifications

Attribute Name Value
Name Turnout
Design vehicles SU-9
Width 2000m
Lateral clearance 0mm
Traveling direction None
Speed 0

Add a Lane

To add a new lane, you can modify road specifications on a specific point. To do this, only the traveled way distribution has to be overloaded on the point.

Traveled Way Distribution

Attribute Name Vlaue
First way center {“Raised median”; 0}
First way right side

{“3.5m lane – OneWay”; 1}
First way left side {“3.5m lane – OneWay”; -1}
Second way center -
Second way right side -
Second way left side -

Road Stretch Specification

A sharp transition can be obtained with the overloading of widening smoothing on the point. The transition starts where the specification is changed. The transition length is given by the specifications.

Attribute Name Vlaue
Design speed -
Category -
Normal slope -
Widening transition -
Widening Smoothing 0m
Second way left side -

Add a Turnout

A turnout can be inserted using the above modelling. For this, two points are required with the specifications as described below.

Shoulder Distribution on Point.1

Attribute Name Vlaue
First way right side

{“Emergency stop strip”; 0}

{“Turnout”; 0}
First way left side {“Emergency stop strip”; 0}
Second way right side -
Second way left side -

Shoulder Distribution on Point.2

Attribute Name Vlaue
First way right side {“Emergency stop strip”; 0}
First way left side {“Emergency stop strip”; 0}
Second way right side -
Second way left side -

Widen a Curve

The swept path width on a curve (U) is calculated using an equation. This equation relies on three more equations: swept path width, width of front overhang and, width of traveled way on curve.

All these equations are considered as exact and are not customizable by Business Rules.

Transition lengths and positions cannot be overloaded at curve level.

Attribute Name Type Value/Description
Curve widening auto Boolean TRUE to compute the value from Eq.1, Eq.2 and Eq.3FALSE to set a user entry
Curve widening Length Computed if the above attribute is set to TRUE
Ratio on inner edge auto Boolen TRUE to compute the value from the lane distribution
Ratio on inner edge Ratio Computed if the above attribute is set to TRUE

Shoulder Superelevation

Shoulder superelevation is computed to satisfy the Roll-over set on the horizontal alignment.

Where the Roll-over is less than the threshold value, the shoulder cross slope is equal to the value set on the horizontal alignment.

On outer edge, where the Roll-over is more than the threshold value, the shoulder cross slope is corrected so that its value is equal to the traveled way superelevation minus the threshold Roll-over.

On inner edge, where the travelway superelevation is more than the shoulder cross slope in tangent, the shoulder cross slope is corrected so that its value is equal to the superelevation value.

You can edit the shoulder superelevation laws from the road surface object to customize those aspects.