Super Elevation Rules

Superelevation Wizard - Overview

The Superelevation Wizard provides a simple approach to the process of applying superelevation to a road.

The superelevation to be applied is based on parameters specified in the rules files. These parameters must be checked to confirm adherence to the appropriate standard.

The process is defined by the following steps:

Step 1

Specify the alignment string for the road to which you wish to add superelevation. You can define the points where you wish superelevation application to start and end. If you wish to apply it along the whole alignment, do not change the start and end fields. You can also select a colour to be used for annotation.

The alignment string must be a master string with an associated geometry string. It must not contain points with null levels over the length to be superelevated.

Step 2

The length to be superelevated can only have one set of parameters applied to it. Therefore a single carriageway which divides to become a dual carriageway must have the superelevation applied separately to the different sections.

Step 3

Set the parameters for superelevation. You can:

specify the design rules and design speed to be used. The design rules will determine whether single or dual carriageway parameters are to be used

select 1 of 6 carriageway pivot options for a single carriageway or 1 of 4 carriageway pivot options for dual carriageways the pivot option selected results in superelevation being applied in different ways.

choose a linear or reverse curve, or biquadratic curve application (by default, only the linear type is available for some pivot methods to avoid potential drainage problems).

Not all pivot options are always available, depending on the rules files being used.

Step 4

Select the carriageway edge strings for the road to which you wish to apply superelevation:

single - specify the left and right edge strings of the carriageway

dual - specify the inner and outer edges of both carriageways.

The carriageway edge strings must not contain points with null levels over the length of road to be superelevated.

Step 5

Before you apply the superelevation you can confirm that the superelevation is correct. To view a list of the conflicts, click Review Conflicts. To correct any conflicts, click Edit to amend the calculated values.

You can also check Create Report to create a text file in the current project folder. The report is created when you click Finish. The report shows how the applied superelevation differs from theoretical values. This report is valuable as an audit record showing how you edited values to resolve conflicts.

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Step 6

Click Finish to apply the superelevation to the carriageway. If you do not want to apply the superelevation click Cancel.

If you select Finish to apply the superelevation, checks are made to determine the existence of other strings associated with the carriageway such as shoulders, hard strips or material edges. If such strings are found, you are asked if you wish to apply superelevation to them. The superelevation is applied to each associated string by extension of crossfall.

If, when calculating the superelevation, the error Error - carriageway has already been superelevated, please redesign carriageway before applying superelevation is displayed, either select other strings to superelevate or click Cancel and redesign the carriageway after using Modify -> Edit Strings -> Delete String Groups to remove the carriageway strings.



Start

This panel lets you select the model and master string for the alignment, set a chainage range over which the superelevation is calculated, and adjust the annotation settings.

Edit Existing allows you to review and edit a previously superelevated roadway. Clicking Edit Existing takes you to the Check Design panel.

Edit Existing is possible because the application method, rules file, speed, strings, application type and pivot method are stored against the model and reference string name. Therefore, if you select the same model and reference string name all the values used to define the superelevation including your edits on the Edit Values panel are loaded to allow efficient access for further edit.



Rules

The superelevation to be applied is based on parameters specified in the rules files. These parameters must be checked to confirm adherence to the appropriate standard.

This panel lets you select the rules you want to use, and select the appropriate design speed.

Many countries have different sets of rules for single and dual carriageway design, which are normally held in separate rules files. You must select an appropriate set of rules for the road you are designing.

Superelevation Rules - Overview



Parameters

This panel lets you select the pivot method you want to use. Additionally you can specify any parameters associated with the Superelevation Application Type such as; linear or Circular Reverse Curve, ease length and the number of lanes where this is required by the rules.

Pivot methods - Single carriageways Pivot methods - Dual carriageways

When a road contains a curve, the profile of the carriageway is superelevated according to the design speed and rules chosen. The way that the cross section changes from the standard profile to the superelevated profile is defined by the pivot method.

When superelevation is applied, the carriageway is rotated about a point on the cross section. This is called the pivot point, and is defined by the pivot method chosen. The following diagram gives an idea of how pivoting works:-

There are four distinct positions along the application length. These are:

Normal Crown - the start of the application length, where the carriageway crossfalls are as defined in the carriageway template, ie, the same as for a straight road.

Level Crown - where adverse camber has been removed, ie, the position at which the crossfall on the outer lane or carriageway becomes flat, having risen up from being negative.

Reverse Crown - where the crossfall on the outer lane of carriageway has risen up past the level crown so that it matches the crossfall of the inner lane or carriageway.

Full Superelevation - where the required superelevation value is achieved.

Depending upon the pivot method being used, not all of these positions will be calculated. For example, if a cross hung single carriageway is pivoted about one of the carriageway edge strings, the level crown position is not calculated, as the road is in the reverse crown stage throughout its length.

This panel also lets you select the way that the string levels will change as the superelevation is applied. For example, if the superelevation is to change from -2½% to 5%, the change in level can be applied at a constant (linear) gradient, by using two equal curves of opposite hand (Symmetrical Reverse Curve) or by using a biquadratic reverse curve.

This example shows the differences between linear, symmetrical reverse curve and biquadratic reverse curve.



For further details of the pivot options, refer to Related Topics.



Single / Dual Carriageway

This panel lets you select the edge strings for the road to be superelevated - two for single carriageways, and four for dual carriageways.

Depending upon the pivot method you have selected, you can also choose to offset the pivot axis from the carriageway edge by checking the Use Offsets from Edge Strings box.

If the string naming convention is in use, the default string names are displayed.

For single carriageways, if the carriageway template uses LC as one of the carriageway edge string names, then this name is displayed as one of the edge string names. Note that pivoting will be about this edge depending on the pivot method selected.

When you click Next the carriageway is checked to determine if it has been previously superelevated. This is determined by comparing the crossfall at the start against the crossfall at each curve. Checking all curves on a long carriageway will take time, therefore the number of curves to be checked can be varied and is specified in the file MfW Road Defaults.ini, which is located in your project's mxdata subfolder.

See Undo Superelevation



Offset Pivots

This panel lets you offset the pivot axis from the left or right carriageway edge of single carriageways, or either of the inner edges on a dual carriageway. You can specify the offset from the reference string or the carriageway edge, and you can vary the offset along the length of the carriageway.

For example, you may want the pivot axis to be at a constant distance from the centre line even when the carriageway edge varies, perhaps because of the addition of a lay-by or junction widening.

Alternatively, it is sometimes required that a dual carriageway is pivoted around the road centre line. There is no option to do this in the Superelevation Wizard (because it can cause excessive cut and fill), but it can be achieved using Offset Pivots. All you need to do is specify the reference string name as the string to offset from, and an offset of zero, for both the left and right carriageways.

To specify an offset, ensure that the appropriate tab is selected, then proceed as follows:

Specify whether you want to measure the offset from the reference string or the carriageway edge by clicking Reference String Name or Left, Right, Inner Edge Name as appropriate.

Specify the offset by using the spinners or typing a value. Remember to click one of the arrow buttons to indicate the direction of the offset.

Define the chainage range over which the pivot axis is to be offset. By default, the start and end chainage of the reference string are supplied. You will need to change these if you want to vary the offset along the length of the string.

Click the Add button.

An entry is added to the table defining the offset to be applied over the chainage range.

To edit an entry, select the entry and click the Update button. The values are returned to the relevant fields in the panel, from where you can edit them. When you have finished, click the Add button once again.

To delete an entry, select the entry and click the Delete button.

Once you have specified all the pivot offsets, click Next.

If you specify varying offsets, you must leave a gap between the chainage ranges which will allow a linear transition to be inserted automatically.

By using offsets to change the pivot axis, you do not change the superelevation applied to the carriageway, but the levels along the new pivot axis are used rather than those at the carriageway edge.



Undo Superelevation

Each time you ask the Superelevation Wizard to calculate and apply superelevation, it checks to see if superelevation has been applied before. If it finds that superelevation has already been applied, it offers you the chance to return the design model to its previous state.

The previous state is the state of the design model before the previous application of superelevation by the Superelevation Wizard. At that time, a copy of the design model was saved as <model name> PRESUPER.

It is therefore recommended that Undo Superelevation is only used if:

you have not progressed to junction design, earthworks and other design options since applying superelevation.

a simple change is required, such as a change of design speed.

If you cannot accept return of the design model to its previous state, yet still wish to change the superelevation, you should reapply the carriageway and shoulder templates to the section of the design model where superelevation needs to be re-applied, then superelevate the section where the templates have been re-applied. You will then have to make sure that the joins between the different sections match the design requirements.



Check Design

This panel lets you apply the calculated superelevation to the carriageway(s). You can review any conflicts that have occurred, by clicking on Review Conflicts, and edit the calculated superelevation by clicking on the Edit button.

Clicking Finish will apply the superelevation and create the Report if the Save Report option is checked.

You can also check Save Report to create a <user named> text file in the current project folder. The report is created when you click Finish. The report shows how the applied superelevation differs from theoretical values. This report is valuable as an audit record showing how you edited values to resolve conflicts.



Superelevate Additional Features

This panel allows you to superelevate additional feature strings associated with the carriageway. If checked, the string group is superelevated by extending the carriageway crossfall.

This panel will only appear if the string naming convention is on and strings of these feature types exist.

The file MFW Road Defaults.ini file (located in your project \MxData subfolder) contains a section called [SuperElevationFeatures] which lists those carriageway features which will be superelevated in addition to the carriageway edges. A typical entry is as follows:

Feature0=CM,0

CM is a partial string name defined in the MXROAD style set (.pss), in this case, Carriageway (Material Edge), and 1 or 0 is a flag which indicates whether the feature will be superelevated by default or not.

In this way, you can superelevate features such as road markings to ensure that they always lie on the road surface.

The feature name is displayed on the panel, rather than the partial string name.

The features you specify should also be included in the carriageway template.

The carriageway edge features (CE, etc) are always superelevated anyway and so do not need to be included in this list.



Edit Values

This panel provides all the tools you require to review or edit the calculated superelevation.

Current Values

This list displays the Current Values to be applied to the superelevation.

A single line in the list can be selected. When a line is selected and highlighted the three tabs on the right hand side of the panel are updated to show the relevant diagram and application details and provide access to the values that can be edited.

When a normal crown or reverse crown line is selected and highlighted the Delete Section icon can be selected to avoid overlapping the adjacent application length. It can also be used to remove a short straight between two curves where it is acceptable to have a smooth superelevation transition between them without having a length of normal crossfall in between. This can also be achieved automatically by setting the appropriate options in the rules files.

The Grade value is the difference in the gradient of the outside edge of the road compared to the gradient of the pivot string. It is also known as the Relative Grade and the Rate of Change. Design standards often state that a maximum, for example 1%, should not be exceeded.

The units used for the Left Slope, Right Slope and Grade columns are shown at the head of the column. The units are set in the Tools -> System Parameters option, on the Analysis defaults tab.

Conflicts

This list displays information about any points along the carriageway where the design is such that the calculated superelevation could cause problems, for example if the calculated length of application is too long for the road to drain properly.

The conflict list is constantly updated as the superelevation is changed in the Current Values tab.

Depending on the settings in the superelevation rule file (.srl) checking is carried out on the resulting gradient calculated from the horizontal transition length. If this gradient is too steep (the application length is too short) the application will not adhere to the comfort criteria. If this gradient is too shallow (the application length is too long) the application will not adhere to drainage criteria.

Where the superelevation design rules result in the superelevation application overlapping from one curve to the next. The display highlights the areas of overlap by changing the colour of the superelevation annotation. The annotation is green on the leading curve and blue on the following curve.

Rules Values

This list displays the calculated values applied. The values do not change and provide a reference.

If you have used the Edit Existing option, this tab is temporarily renamed Original Values because the values may not be the same as the original rules values.

Diagram

This tab displays a schematic diagram showing a curve and the selected section type highlighted in red.

Clicking on any item in the Current Values list brings up a schematic diagram of the curve, with crossfall wedges showing how the superelevation is applied. Each curve on the alignment will have two, four or six values calculated, depending on the pivot method used. The diagram also shows which point is selected by highlighting it in red.



Edit

To edit the values for a particular point (for example, Reverse Crown In), click on the appropriate line in the Current Values list. Select the Edit tab. The relevant description is shown in red. Depending upon the rules you have selected, you can edit either Chainages and Crossfalls or Application Length. Click the appropriate radio button.to display the values that may be edited.chainage

Chainages and Crossfalls

Select the Chainages and Crossfalls radio button. The relevant description for the point highlighted in the Current Values list is shown in red and its values may be edited. Edit either the chainage or slope value then click Apply.

As you edit the values click Apply You can then see the results in the plan view, and confirm that a conflict has been resolved by selecting the Conflicts list. As soon as you click Apply, the changes are made and the Undo button is made available.

Application Length

There are two ways of modifying the Application Llength; you can edit its value or slide the length along the curve.

To edit the application length select the Application Length radio button, then define the type of modification by selecting either Edit Application Length or Slide Application Length.

To edit using Edit Application Length specify a new value and then indicate whether the length is to be locked at the full superelevation or normal crown position, or whether the length is to be changed equally at both ends.

To edit using Slide Application Length, specify the distance and then whether the application is to be moved in a forward or reverse direction along the string.

The individual length values denote the distance between the point you select and the previous point, for example, the reverse crown and the normal crown points.

As you edit the values click Apply You can then see the results in the plan view, and confirm that a conflict has been resolved by selecting the Conflicts list. As soon as you click Apply, the changes are made and the Undo arrow is no longer greyed.

Superelevation with reverse crowns verifies that the application length is not less than the length between the normal crown and the reverse crown. If the length is less than the length between the normal crown and reverse crown the calculated value is retained.

Where the superelevation design rules result in the superelevation application overlapping from one curve to the next. The display highlights the areas of overlap by changing the colour of the superelevation annotation. The annotation is green on the leading curve and blue on the following curve.

Application Details

This tab displays the following read-only information about the superelevation applied to the selected curve.

Rules - the name and location of the superelevation rules file applied.

Design Speed - value applied

Pivoting Option - number

Superelevation Application - schematic and method, for example linear, symmetrical reverse curve, and biquadratic reverse curve.

Rate of Change Calculation/ Grade



To calculate the Rate of Change displayed as Grade on the Current Values tab::

Find the width of a lane at the curve, for example 3.65 metres for a ?? single carriageway.

Calculate the level difference between the centre line and the outside channel, at the crossfall quoted for both ends of the application length. For example, a crossfall of -2.5% over 3.65 metres would give a level difference of -0.09125 metres. A crossfall of +7% would give a level difference of +0.255 metres.

Add the two level differences together. -0.09125 + 0.255 = 0.34675 metres.

The Rate of Change is given by (1 / sum of level differences) x application length. For example (1 / 0.34675) x 30 = 86.52 1 in N.

The Rate of Change will alter if the application length is changed, or the full superelevation crossfall is changed in the Superelevation Editor.

The Rate of Change is always calculated for the outer channel - the channel with the biggest change.

Clicking Finish will apply the superelevation and create the Report if the Save Report option is checked.

You can also click Save Report to create a <user named> text file in the current project folder. The report is created when you click Finish. The report shows how the applied superelevation differs from theoretical values. This report is valuable as an audit record showing how you edited values to resolve conflicts.



Application of Levels

For some of the pivot methods, it can be seen that to apply superelevation to a road, the levels on the master string would have to be amended.

For single carriageways, this situation occurs when pivoting is done about either of the carriageway edge strings.

For dual carriageways, it can apply when pivoting about the edges of the central reservation. This allows the central reservation to be vertically offset from the master string.

This is not desirable, as the master string would become `out of step' with its associated geometry string, and the alignment from which they were created. This problem is overcome by the Superelevation Wizard which creates a centre line level string, if one does not already exist, which is stored in the design model when you accept the superelevation.

It is important that you are aware that the master string may not lie on the design surface when using other MX options, such as creating cross sections. The MXROAD options take care of this automatically, and provide a selection mask file that can be used throughout MX, to ensure that the correct strings are being used.



Pivot Options - Overview

When a road contains a curve, the profile of the carriageway is superelevated according to the design speed and rules chosen. The way that the cross section changes from the standard profile to the superelevated profile is defined by the pivot method.

When superelevation is applied, the carriageway is rotated about a point on the cross section. This is called the pivot point, and is defined by the pivot method chosen. The following diagram gives an idea of how pivoting works:

Pivot methods - Single carriageways Pivot methods - Dual carriageways

There are four distinct positions along the application length. These are:

Normal Crown - the start of the application length, where the carriageway crossfalls are as defined in the carriageway template, ie, the same as for a straight road.

Level Crown - where adverse camber has been removed, ie, the position at which the crossfall on the outer lane or carriageway becomes flat, having risen up from being negative.

Reverse Crown - where the crossfall on the outer lane of carriageway has risen up past the level crown so that it matches the crossfall of the inner lane or carriageway.

Full Superelevation - where the required superelevation value is achieved.

Depending upon the pivot method being used, not all of these positions will be calculated. For example, if a cross hung single carriageway is pivoted about one of the carriageway edge strings, neither the normal or level crown positions are calculated, as the road is in the reverse crown stage throughout its length.

For further details of the pivot options, refer to Related Topics.



Pivot methods - Single carriageways

Each of the following define the pivot point location, and method of application. For more information about each pivot method, click the schematic.


Single - centre line pivot, cambered road

This pivot method pivots the carriageway about the centre line, on a cambered road. The application of superelevation to the left and right carriageway edge strings will start (or end) at different chainages, to ensure that the rate of change remains the same for both strings. Only the linear method of application is available, to avoid possible drainage problems.

For a right hand curve superelevation is applied as shown below:

Key

A = Normal Crown

B = Level Crown

C = Reverse Crown

D = Full Superelevation

Depending on the rules files being used, the level crown position may not be output, and the reverse crown may be read-only, ie, its position cannot be adjusted.

Single - centre line pivot, cross-hung road

This pivot method pivots the carriageway about the centre line, on a cross-hung road. The application of superelevation to the left and right channel strings will start (or end) at the same chainages, so the rate of change of each string is different. All three application methods (linear, symmetrical reverse curve, and biquadratic reverse curve) are available.

For a right hand curve superelevation is applied as shown below:-



Key

A = Normal Crown

B = Reverse Crown

C = Full Superelevation

Single - inside edge pivot (rising) cambered road

This pivot method pivots about the carriageway edge string on the inside of the curve.

With this pivot method the level string (LC) has superelevation applied to it, the master string does not. This is done as the master string would otherwise become `out of step' with its associated geometry string, and the alignment from which they were created.

The application of superelevation will start (or end) at different chainages, to ensure that the rate of change remains the same for both strings. Only the linear method of application is available, to avoid possible drainage problems.


For a right hand curve, superelevation is applied as shown below:

Key

A = Normal Crown

B = Level Crown



C = Reverse Crown


Single - inside edge pivot (rising) cross-hung road

This pivot method pivots the carriageway about the carriageway edge string on the inside of the curve on a cross-hung road. The application of superelevation to the centre line and left channel strings will start (or end) at the same chainages, so the rate of change of each string is different. All three application methods (linear, symmetrical reverse curve, and biquadratic reverse curve) are available.



For a right hand curve, superelevation is applied as shown below:

Key

A = Normal Crown

B = Reverse Crown


Single - outside edge pivot (lowering) cambered road

This pivot method pivots the carriageway about the carriageway edge string on the outside of the curve on a cambered road.

The application of superelevation will start (or end) at different chainages, to ensure that the rate of change remains the same for both strings. Only the linear method of application is available, to avoid possible drainage problems.





For a right hand curve, superelevation is applied as shown below:-

Key

A = Normal Crown

B = Level Crown

C = Reverse Crown


Single - outside edge pivot (lowering) cross-hung road

This pivot method pivots the carriageway about the carriageway edge string on the outside of the curve on a cross-hung road. The application of superelevation will start (or end) at the same chainages, so the rate of change of each string is different. All three application methods (linear, symmetrical reverse curve, and biquadratic reverse curve) are available.



For a right hand curve, superelevation is applied as shown below:-



Key

A = Normal Crown

B = Reverse Crown




Pivot methods - Dual carriageways

Each of the following define the pivot point location, and method of application. For more information about each pivot method, click the schematic.


Dual - inner edge pivot of both carriageways different chainage

This pivot method pivots the dual carriageway about the inner edge strings of both carriageways using different chainage, so the central reservation levels are not changed. The application of superelevation to the left and right carriageways will start (or end) at different chainages, to ensure that the rate of change remains the same for both. All three application methods (linear, symmetrical reverse curve, and biquadratic reverse curve) are available.

When using dual carriageway pivot methods, the levels on the centre line level string and any other central reserve strings (with the exception of carriageway edges) may not be modified according to the superelevation. Consequently, when viewed as cross sections, the central reserve kerbs and surface may be displayed incorrectly. Use Design -> Design a String -> Extension of Crossfall to modify the incorrect strings.


Key

A = Normal Crown

B = Level Crown

C = Reverse Crown


Dual - inner edge pivot of both carriageways same chainage

This pivot method pivots the dual carriageway about the inner edge pivot of both carriageways using the same chainage, so the central reservation levels are not changed. The application of superelevation to the left and



right carriageways will start (or end) at the same chainages, so the rate of change of each carriageway is different. All three application methods (linear, symmetrical reverse curve, and biquadratic reverse curve) are available.



Key

A = Normal Crown

B = Reverse Crown


Dual - inner/outer pivot of the left/right carriageways different chainages

This pivot method pivots the dual carriageway about the inner edge of the left hand carriageway, and the outer edge of the right hand carriageway for right hand curves. Pivot the dual carriageway about the outer edge of the left hand carriageway, and the inner edge of the right hand carriageway for left hand curves.

Levels on the central reservation will change to accommodate the superelevation of the carriageways. The application of superelevation to the left and right carriageways will start (or end) at different chainages, to ensure that the rate of change remains the same for both. All three application methods (linear, symmetrical reverse curve, and biquadratic reverse curve) are available.





Key

A = Normal Crown

B = Reverse Crown


Dual - inner/outer pivot of the left/right carriageways same chainage

This pivot method pivots the dual carriageway about the inner edge of the left hand carriageway, and the outer edge of the right hand one. Levels on the central reservation will change to accommodate the superelevation of the carriageways. The application of superelevation to the left and right carriageways will start (or end) at the same chainages, so the rate of change of each carriageway is different. All three application methods (linear, symmetrical reverse curve, and biquadratic reverse curve) are available.



Key

A = Normal Crown



B = Reverse Crown




Superelevation rules - overview

A major feature of MXROAD is the automatic application of superelevation to carriageway strings according to a set of design rules. The superelevation rules incorporate national or local standards, and rules can be modified to allow for local variations from national standards. Rules consist of tables of criteria and user defined formulae.

The rules are assembled in a series of external text files which are prepared outside of MX. There are six files as follows:

<filename>.srl - the main rules parameter file. <filename>.sel - the crossfall rules to be applied to carriageways. <filename>.trl - the superelevation changeover lengths for transitions. <filename>.ntl - the superelevation changeover lengths when there are no transitions. <filename>.ckl - the transition lengths check table. <filename>.sgl - the lengths required for special geometry. <filename>.ssl - the lengths required for short straights. <filename>.sal - the lengths required for early starts or steepening the application. <filename>.ntp - the no transition position rules

For any set of design rules, the sel and srl files must exist but the other files are optional.

If the design rules vary for different road types, each road type must have its own set of rules files, though these can be shared if the name of the file is defined in the rules parameter file (.srl).

The features of the design rules are:

the rules adhere to national standards but can be modified if necessary.

equations and look-up tables are used within the rules to calculate the amount, type and length of application of superelevation to apply for a specified design speed and radius of curve.

Other factors can be taken into account if required, such as the number of lanes, lane width, channel gradient etc.

superelevation may be applied on all or part of a transition, and the location of the application may be specified relative to the curve.

superelevation may be applied when no transitions exist.

removal of adverse camber before the start of a transition may be incorporated.

superelevation may be applied across circular curves of the same or opposite hand (`C' or `S' curves) according to defined criteria.

the parts of the alignment where superelevation is applied are checked to ensure that they do not overlap.



Superelevation rules - key to variables

This topic describes the variables used in the rules files.

Equations

The following variables can be used in the equations in the rules files. They may be found in both the equations section, in which case they are followed by an exclamation mark, or in the table section.

Table of conditions

For example, in the following table,

| 120.000| 510.000| 5.0| | 120.000| 200.000| O 7.0| | 120.000| 0.000| X |

the Superelevation Wizard would apply a crossfall of 7% to any curve of radius 200 to 509.999 metres. If this happens, a message is sent to the conflict table saying that the overriding value has been used.

Similarly, in the following table,

| 120.000| 300.000| 5.0| | 120.000| 200.000| I 7.0| | 120.000| 0.000| X |

* - comment line

r - Radius of curve

v - Design speed

nc - Number of carriageways (single carriageway = 1, dual carriageway = 2)

wc - Width of carriageway, ie, the width of one side of the road (e.g from centre line to channel for a single carriageway, and outer channel to inner channel for a dual carriageway). Equals the number of lanes (nl!) times the width of a lane (wl!).

nl - Number of lanes

wl - Width of lane

w - Width from current pivot string to outer edge of carriageway

s - Superelevation calculated for the curve (in %).

ds - Change in superelevation (the difference between the crossfall of the unsuperelevated road (e.g. -2.0%) and the superelevated curve (e.g. 5.0%) giving a ds! of 7.0%)

lcf - Linear/curve factor (lcf! = 1 for linear application, lcf! = 2 for reverse curve application)

tl - Transition length

al - Application length

N - no change to the template value

E <n> - use equation <n>

G <n> <m>

- use the greater of equation <n> or <m>

L <n> <m>

- use the lesser of equation <n> or <m>

<value> - use the numerical value given

X - the combination of speed and radius is invalid, so report an error

R - reverse crossfall (equal to the normal crossfall but positive in sign)

O - override radius - specify this to apply a crossfall to a curve which would otherwise require a re-design, or a lowering of the design speed.

I - use linear interpolation to calculate values for superelevation when the specified value (usually radius) is not present.



the Superelevation Wizard would apply a crossfall of 6% to any curve of radius 250 metres.



Superelevation rules parameter file (*.srl)

This file defines the basic parameters to be used by the design rules.

Click the appropriate subject to see details of a section.

Superelevation rule file to be used Superelevation application (curves with transitions) Superelevation application (curves without transitions) Early start of application Steepen application Application Length Rounding Chainage rounding Superelevation overlap Application method Minimum Ease Length Transition length check S and C curve alignment geometry Design speed Short Straight

The files are located in the public styles folder in the MX installation structure.

Notes

If a line starts with an `*' it is a comment line.

Characters 1 to 20 of a line contain the variable name used by the program. This MUST NOT be altered.

Characters 21-52 contain the default value applied to the variable. This value may be amended.

Characters 53-80 contain descriptive text. The easiest way to create a new set of parameters is to take a copy of a superelevation rules parameter file (*.srl) supplied with your MX installation and edit it.

Superelevation rule file to be used

If these parameters appear in this file then the file name specified will be used. These files must exist in the same styles folder as the superelevation rules parameter file (*.srl) that calls them. If they are not specified, then a file with the same prefix as the superelevation rules parameter file (*.srl) will be used.

Not all rules files have to be used. For example, if your standards dictate that you do not need to check for comfort and drainage criteria, then you can disable this check in the superelevation rules parameter file (*.srl) so that you do not need a check application length rules file (*.ckl).

Superelevation value rules file (rule_file_sel$)

This variable defines the name of the superelevation value rules file (*.sel).

Transition application length rules file (rule_file_trl$)

This variable defines the name of the transition application length rules file (*.trl).

No transition application length rules file (rule_file_ntl$)

This variable defines the name of the no transition application length rules file (*.ntl).

Check application length rules file (rule_file_ckl$)

This variable defines the name of the check application length rules file (*.ckl).



Special geometry curves application length rules file (rule_file_sgl$)

This variable defines the name of the special geometry curves application length rules file (*.sgl).

Superelevation short straight length rules (rule_file_ssl$)

This variable defines the name of the superelevation short straight length rules file (*.ssl)

Early start or steepen application length rules (rule_file_sal$)

This variable defines the name of the early start or steepen application length rules file (*.sal)

No transition position rules (rule_file_ntp$)

This variable defines the name of the no transition position rules file (*.ntp)

Carriageways (num_carriageways%)

This defines whether the rule file is for a single or dual carriageway, and therefore determines whether you will be prompted for two or four edge strings. It can have the following values:

1 - single carriagway

2 - dual carriageway

Pivot methods (pivot_method_1$ to pivot_method_6$)

These variables control the pivot methods available for the rules selected. If N (disallowed) is used then the pivot method will be greyed out in the Select Pivot method panel. Specify Y to allow a pivot method.

Superelevation application (curves with transitions)

Transition superelevation length (tr_sup_len%)

The superelevation application on transitions can be applied either over a calculated length, the exact length of the transition or a fraction of it. If the calculated length option (1) is used, the associated .trl file must exist.

The variable can have the following values:

1 - apply over a calculated length using rules file (*.trl)

2 - apply over the transition length

3 - apply over a factor of the transition length (see next variable)

Transition factor (tr_fact_len!)

If the transition factor option (3) is used in tr_sup_len%, the factor is defined here as a real value, for example, 0.8.

Transition superelevation position (tr_sup_pos%)

The end of the length of application does not always finish at the start of the curve following the transition. The superelevation can be shifted so that some of it is applied on the curve.


1 - at start/end of curve

2 - 1/3 on the curve




4 - wholly on curve

5 - fixed distance on the curve (see tr_pos_dist! below)

6 - percentage on curve (see tr_pos_dist! below)

If option (5) or (6) is used, the amount of superelevation applied on the curve is defined in the next entry.

Transition superelevation distance (tr_pos_dist!)

This variable can have the following values:

Fixed distance as a real number, eg, 10.0. (option 5 above)

Percentage on curve as a real number, eg, 10.0 (option 6 above)

Superelevation application (curves without transitions)

The following four entries are similar to those for curves with transitions but apply to curves which have no associated transitions. If the calculated length option (1) is used, the associated .ntl file must exist.

No transition superelevation length (notr_sup_len%)


1- apply over a calculated length using rules file (*.ntl)

2 - apply over a fixed length (see next variable)

3 - give warning

Fixed length (notr_fix_len!)

If the transition fixed length option (2) is used in notr_sup_len%, the length is defined here as a real value, for example, 30.

No transition superelevation position (notr_sup_pos%)

The end of the length of application does not always finish at the start of the curve. The superelevation can be shifted so that some of it is applied on the curve.


1 - at start/end of curve



4 - wholly on curve

5 - fixed distance on the curve (see notr_pos_dist! below)

6 - percentage on curve (see notr_pos_dist! below)

7 - calculate according to the *.ntp rules file.

If option (5) or (6) is used, the amount of superelevation applied on the curve is defined in the next entry.

No transition superelevation distance (notr_pos_dist!)

This variable can have the following values:



Fixed distance as a real number, eg, 10.0. (option 5 above)

Percentage on curve as a real number, eg, 10.0 (option 6 above)

Early start of application

For cambered single carriageway pivot methods, adverse crossfall can be removed before the application of superelevation by applying an early start.

Early start indicator (early_start_ind%)

This variable defines whether an early start of application is used, and, if so, where the application begins.

If no transition exists, the length defined in the Changeover Lengths without Transitions file (*.ntl) is used rather than the transition length.

For early start indicator values of 0, 1 and 2, you can change the rate of application of superelevation by setting the steepen application indicator (steepen_app_ind%) .


Early start indicator = 0

No early start, the superelevation is applied over the length of the transition.

T = Transition E = Curve A = Normal Crown B = Level Crown C = Reverse Crown D = Full Superelevation


The superelevation is started early so that a level crown occurs at the start of the transition.



The superelevation is started early so that a reverse crown occurs at the start of the transition.





The superelevation is started early so that a level crown occurs at the start of the transition, but the distance between normal crown and level crown is user-definable (see below). This means that the rate of change of application between the normal crown and level crown is different from that between the level crown and full superelevation.

T = Transition E = Curve l = Early Start Length A = Normal Crown B = Level Crown C = Reverse Crown D = Full Superelevation


The superelevation is started early so that a reverse crown occurs at the start of the transition, but the distance between normal crown and reverse crown is user-definable (see below). This means that the rate of change of application between the normal crown and reverse crown is different from that between the reverse crown and full superelevation.

T = Transition E = Curve l = Early Start Length A = Normal Crown B = Level Crown C = Reverse Crown D = Full Superelevation




As for early start indicator = 1 but using the rules (*.sal) file.


As for early start indicator = 2 but using the rules (*.sal) file.

Early start length (early_start_len!)

This variable defines the distance used by the early start methods 3 and 4 above.

Steepen application

For all pivot methods, you can change the rate of change of application of superelevation. By default, ie, with no steepening, the rate of change is constant over the application length. With steepening, the rate of change is constant between normal crown and reverse crown, changes at reverse crown, then remains constant until full superelevation.

Steepen application is only valid if the early start indicator is 0, 1 or 2.

Steepen application indicator (steepen_app_ind%)

This variable defines whether steepening is used. It can have the following values:

0 - no steepening is applied

1 - steepening is applied over a defined length

2 - steepening is applied according to the rules unless the calculated length exceeds a specified maximum, in which case the maximum is used.

3 - defined length from rules file (*.sal)

4 - maximum length from rules file (*.sal)

The effects of the variable differ depending upon the value of the early start indicator (early_start_ind%) as follows:

Early start indicator = 0 Steepen application indicator = 1, 2, 3 or 4

No early start, so the superelevation is applied over the length of the transition, but the superelevation reaches the reverse crown stage sooner than it would without steepening.

T = Transition E = Curve S = Steepen Application Length A = Normal Crown B = Level Crown C = Reverse Crown D = Full Superelevation




An early start is applied, so the superelevation is applied before the transition, and the superelevation reaches the level crown stage at the start of the transition.



An early start is applied, so the superelevation is applied before the transition, and the superelevation reaches the reverse crown stage at the start of the transition.


Steepen application length (steepen_app_len!)

This variable defines the steepening length, which can be the actual length or a maximum length depending upon the value of steepen_app_ind%.

Note that the length you specify is the distance between the normal crown and level crown. This is half the distance between the normal and reverse crown.

For example, if the calculated distance from the normal to reverse crown is 40m, and you want to use a defined length of 30m, you should specify steepen_app_ind% = 1 and steepen_app_len! = 15m. If the calculated distance is 20m, the defined length of 30m will still be used.

Similarly, if the calculated distance from the normal to reverse crown is 40m, and you want to use a maximum of 30m, you should specify steepen_app_ind% = 2 and steepen_app_len! = 15m. If the calculated distance is 20m, 20m will be used as it is less than the maximum length of 30m.



Note that the actual or maximum lengths given above could be calculated from the *.sal file.

Application Length Rounding

The length of superelevation application, given in the superelevation changeover length rules (*.trl) file, can be rounded to simplify construction of the carriageway. The length can be rounded up, down or to the specified interval, for example 5 or 10m.

Application length rounding (app_len_round%)

This variable defines the rounding of the application length and can have the following values:

0 - no rounding

1 - round up

2 - round down

3 - round to the nearest, ie, up or down.

Application length rounding interval (app_len_round_int%)

This variable defines the interval to which to round the application length, for example 5 or 10.

The interval value entered will be treated as an integer.

Chainage rounding

Both the start and end chainage of superelevation application can be rounded to simplify construction of the carriageway. Chainages can be rounded up, down or to the nearest specified interval, for example, 5 or 10m.

Chainage rounding is not applied to the level and reverse crown chainages, as they are a result of the calculation. Rounding the start and end chainages will therefore affect the application length.

Start chainage rounding (start_round%)

This variable defines the rounding of the start chainage and can have the following values:

0 - no rounding

1 - round up

2 - round down


Start chainage interval (start_round_int%)

This variable defines the chainage interval to round the start chainage to, for example, 5.

End chainage rounding (end_round%)

This variable defines the rounding of the end chainage and can have the following values:

0 - no rounding

1 - round up

2 - round down




End chainage interval (end_round_int%)

This variable defines the chainage interval to round the end chainage to, for example, 5.

Superelevation overlap

Superelevation overlap indicator (overlap%)

If two lengths of application are close, there is the possibility that they will overlap. If this happens, a message is displayed in the conflict table which you may define as a conflict or a warning. If you define overlap as a conflict, the carriageway will not be superelevated.


0 - give warning

1 - give conflict

Application method

Superelevation application indicator (sup_method%)

Superelevation may be applied linearly, as a symmetrical reverse curve or as a biquadratic curve.


1 - linear

2 - symmetrical reverse curve

4 - circular reverse curve

5 - biquadratic curve

Transition length check

Transition length check indicator (tr_check%)

The lengths of transitions in the alignment can be checked against the theoretical lengths calculated from the design rules using the lower or upper factors specified.


0 - no checking

1 - give conflict using rule file *.ckl.

2 - give warning using rule file *.ckl.

3 - checks that the longitudinal gradient of the edge of road features is not less than a defined slope. If tr_check% is set to 3, annotation is added to the display if the longitudinal gradient is less than the minimum, or greater than the maximum allowed, to highlight the length of road edge affected. In the case of the minimum slope, it should be noted that this may not be within a length of superelevation application - it could be anywhere along the length of road being superelevated. On a dual carriageway, this check is done on both the inner and outer road edges. The conflicts panel will also include the chainages at which this problem occurs, and any locations where the rate of change of the road edge is greater than the maximum allowed.

If tr_check% is set to 1 or 2, then:



Upper check limit (tr_check_upper!)

This value is a factor of the transition length, for example, 1.0.

Lower check limit (tr_check_lower!)

This value is a factor of the transition length, for example, 0.75.

If tr_check% is set to 3, then:

Upper check limit (tr_check_upper!)

This value is the maximum rate of change of grade of the road edge relative to the feature that the road is superelevated about (e.g. the road centre line) in percent, for example, 1.0.

Lower check limit (tr_check_lower!)

This value is the minimum longitudinal gradient in percent, for example, 0.5.

These two check values are generally termed comfort, drainage or appearance values.

Where tr_check% = 1 and 2. If the value exceeds the upper limit, the conflict message `The application length is too long for the drainage criteria' is given.

Where tr_check% = 3. A conflict message is given if the slopes are greater or less than the specified values..

Where tr_check% = 3. The slope in the conflict message is shown in the units specified in Tools -> System Parameters.

Minimum Ease Length

Ease will be applied to curves where the Superelevation Application Type is Circular Reverse Curve. Ease is achieved by the application of vertical circular reverse curves with a straight between the curves.

Minimum Ease Length (min_ease_length!)

This value is the application vertical reverse curve minimum length, for example 20.

Depending on the length of application and the ease length specified not all applications will be long enough to allow the ease, so these applications will revert to Linear and a conflict will be given.

S and C curve alignment geometry

Certain types of geometry can be disallowed and a conflict message given.

S curve with transitions (tr_s_curve%)

This variable indicates how superelevation is applied for S curves with transitions:

0 - not allowed, give conflict message

1 - apply over transition length

2 - apply over a calculated length using the rules file *.sgl.

S curve with transitions (tr_s_curve_pro%) - profile shape

This variable indicates how superelevation is applied for S curves with transitions at the inflection point:

0 - flat at calculated point



1 - template profile at inflection point

2 - flat at inflection point

S curve without transitions (notr_s_curve%)

This variable indicates how superelevation is applied for S curves without transitions:


1 - apply over a calculated length using the rules file *.ntl

2 - apply over a calculated length using the rules file *.sgl.

C curve with one transition (tr_1_c_curve%)

This variable indicates how superelevation is applied for C curves with one transition:



C curve with two transitions (tr_2_c_curve%)

This variable indicates how superelevation is applied for C curves with two transitions:



C curve without transitions (notr_c_curve%)

This variable indicates how superelevation is applied for C curves without transitions:


1 - apply over a calculated length using the rules file *.ntl

Design speed

These parameters control the design speeds available from the Rules panel. They should match the speeds defined in the other rules files, for example the .sel (superelevation file) etc

Default design speed indicator (def_speed%)

This variable defines which of the design speed variables below is used as the default, for example, 1 in this case would be a default design speed of 120kph.

Design speeds (speed_1% to speed_99%)

These variables contain the available design speeds, for example: speed_1% - 120 speed_2% - 90 speed_3% - 70 speed_4% - 50

A speed value of 0 indicates an unused speed field.

Short Straight

This variable is used to control the handling of short straight elements found between adjacent curves of the



same hand ('C') and of opposite hand ('S').

Short straight indicator S (short_strai_ind_s%) - value

This variable indicates how superelevation is applied for S curves separated by a short straight:

0 - OFF

1 - On, replace with S curve application.

3 - Use rules file to determine maximum straight length (*.ssl), and replace straight with s curve application.

4 - On minimum length, advise conflict only.

6 - Use rules file to determine maximum straight length (*.ssl), advise conflict only.

Short straight indicator C (short_strai_ind_c%) - value

This variable indicates how superelevation is applied for C curves separated by a short straight

0 - OFF

1 - On, replace with C curve application.

2 - Use rules file for Reverse Crown radius (*.ssl), replace with C curve application.

3 - Use rules file to determine maximum straight length (*.ssl), and replace straight with C curve application.

4 - On minimum length, advise conflict only.

6 - Use rules file to determine minimum straight length (*.ssl), advise conflict only.



Carriageway superelevation rules (*.sel)

This file defines how the superelevation changes are applied. The file consists of a series of equations followed by a table of conditions detailing which equation is to be applied and when.

Click here to see the key to the variables used in equations and tables.

Equations Table of conditions

Superelevation equations

The equations defined in this section may be fixed values or equations with variables. The equations calculate the numerical value to be used. An example of the equation list is:

E 1 3750.0/r! E 2 14.0-3.141592654*0.434294481*log(r!) E 3 5.0 E 4 7.0 E 5 8.0

Notes

E 1 is the equation number.

3750.0/r! is the first equation.

E 3 to E 5 are explicit values of percentage superelevation.

Blank lines are not allowed between equations.

Rounding

If an equation is used its result can be rounded. For example, an equation might be of the form v!*v!/(2.828*r!). This would calculate the superelevation without any rounding, e.g. 0.0326 or 3.26%.

To round the superelevation to one decimal place (e.g. 0.033 or 3.3%), use: int((v!*v!/(2.828*r!)*10)+0.5)/10

To round the superelevation to half a percent (e.g. 0.035 or 3.5%), use: int((v!*v!/(2.828*r!)+0.25)*2)/2

To round the superelevation to the nearest whole number (e.g. 0.03 or 3%), use: int(v!*v!/(2.828*r!)+0.5)

Table of conditions

T C=3;C1=v;C2>r * +-------------+-------------+----------+ * | Speed | Radius | Super | * +-------------+-------------+----------+ | 120.000| 4000.000| N| | 120.000| 1500.000| 2.5| | 120.000| 749.999| L 1 3| | 120.000| 0.000| X| | 90.000| 2000.000| N| | 90.000| 700.000| 2.5| | 90.000| 319.999| L 2 4| | 70.000| 800.000| N| | 70.000| 365.000| 2.5| | 70.000| 169.999| L 2 4| | 70.000| 0.000| X| | 50.000| 300.000| N| | 50.000| 160.000| 2.5| | 50.000| 84.999| L 2 5| | 50.000| 79.999| 8.0|+ | 50.000| 0.000| X|



* +-------------+-------------+----------+

Notes

T C=3;C1=v;C2>r is the table interpretation code. C = 3 indicates the table is a 3 column table. C1 = v indicates the first column is design speed. The `=' indicates that the v value must be exactly matched somewhere in the column. If it is not, an error is given. C2 > r indicates the second column contains a range of radius values (C2 = r would indicate the second column has superelevation applied for specified radii only.)

Column 1 a set value for design speed.

All the design speeds you may use within the design should be listed. If, at the time of calling the rules, a design speed is given that is not in this list then an error is given.

This column contains real numbers of up to 13 digits, with 3 decimal places.

Column 2 a set value for the radius.

The equation quoted in column 3 applies to this radius and all other radii up to the radius given on the line above. For example, the line with the radius 1500.000 will have a superelevation value of 2.5% applied between 1500.000m and 3999.999m.

This column contains real numbers of up to 13 digits, with 3 decimal places.

Column 3 the equation code to be used.

This column contains up to 10 alphanumeric characters.

All information given in the columns should be right justified.

The change of superelevation is applied according to the method defined in the parameter file. The methods are:

linear

reverse cubic curve

reverse biquadratic curve.

The easiest way to create a new set of superelevation rules is to take copies of the appropriate files supplied with MX and edit them.

The default file is located in the public styles folder in the MX software structure.



Superelevation changeover length (with transitions) rules (*.trl)

This file defines the length over which the change in superelevation is applied, when the alignment contains transitions. It is only used if the variable tr_sup_len% in the superelevation rules parameter file *.srl is set to 1.

The length given is always the longest length of change. It is measured along the line of the alignment and usually corresponds to the change applied to the outer carriageway edge.



Superelevation changeover length (without transitions) rules (*.ntl)

This file defines the length over which the change in superelevation is applied, when the alignment does not contain transitions.

The length given is always the longest length of change. It is measured along the line of the alignment and usually corresponds to the change applied to the outer carriageway edge.



Transition lengths check table (*.ckl)

This file is required if the designed transition lengths are to be checked against the lengths calculated for the required superelevationsuperelevation changes.

The structure of the file is very similar to the superelevation file (.sel) in that the first part of the file consists of equations to be used followed by the table of conditions in which they apply.

Only one column of information is required for this file, therefore the table interpretation code is T C=1.

Column 1 blank

This column contains 13 spaces.

Column 2 blank.

This column contains 13 spaces.

Column 3 the equation code to be used.

This column contains up to 10 alphanumeric characters.


The easiest way to create a new set of transition check length rules is to take a copy of a *.ckl file supplied with your MX installation and edit it.




Special geometry check table (*.sgl)

This file is required to calculate transition lengths for S and C curve geometry.

The structure of the file is very similar to the superelevation file (.sel) in that the first part of the file consists of equations to be used followed by the table of conditions in which they apply.


The easiest way to create a new set of special geometry check length rules is to take a copy of a *.sgl file supplied with your MX installation and edit it.




Superelevation short straight length rules (*.ssl)

C Curve

This file defines the radius at which the reverse crown occurs on a transition for same hand ('C') curves. It is only used if the variable short_strai_ind_c% in the superelevation rules parameter file *.srl is set to 2, 3, and 4.

Normally, the position of the reverse crown is calculated as a result of the superelevation application length, but this variable allows you to specify its position according to a formula or table.

This file has a second use. It determines if the length of a straight is less than the value obtained from this file. This occurs if the variable short_strai_ind_c% in the superelevation rules parameter file *.srl set to 6.

S Curve

This file defines the radius at which the reverse crown occurs on a transition for opposite hand ('S') curves. It is only used if the variable short_strai_ind_s% in the superelevation rules parameter file *.srl is set to 2, 3and 4.

Normally, the position of the reverse crown is calculated as a result of the superelevation application length, but this variable allows you to specify its position according to a formula or table.

This file has a second use. It determines if the length of a straight is less than the value obtained from this file. This occurs if the variable short_strai_ind_s% in the superelevation rules parameter file *.srl set to 6.



Early start or steepen application length rules (*.sal)

This file defines the early start or steepen application length. It is only used if the variable early_start_ind% is set to 5 or 6 or the variable steepen_app_ind% is set to 3 or 4 in the superelevation rules parameter file *.srl.

Normally, the length used is a fixed value but some superelevation standards require it to vary with, for example, the design speed.



No transition position rules (*.ntp)

This file defines the amount of the superelevation application length which is put on a straight when there is no transition, ie, when curves are joined to straights without a transition. It is only used if the variable notr_sup_pos% is set to 7 in the superelevation rules parameter file *.srl.

Normally, the amount of application length placed on the straight is a fixed value, for example, 70%, but some superelevation standards require it to vary with, for example, the design speed.



Ease

Ease is the method used in Australia by both the RTA and AUSTROADS standards. Similar techniques may be used elsewhere in the world to achieve similar results.

The figure 2.2.2 (shown below) of the Road Design Guide Section 2 shows what is described as an "ease." You can request Ease by using the "Circular Reverse Curve (Ease)" option on the Superelevation Wizard: Parameters panel.

Ease applies circular reverse curves to a defined length to smooth the transition between the crossfall on the straight, and the application of superelevation.

A default Ease Length is stored in the rules file, but it can be overridden if required.

Ease has been implemented for single carriageways only.

A message is given in Conflicts if an ease cannot be fitted, and a Linear application is used instead.



Super Elevation Rules

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