Grade

The Grades tab specifies the uphill and downhill grade parameters to be used in a geometry type. Tables can be used to specify ranges for the grade in each direction as well as the maximum length the average grade needs to be met. Here you are able to enter a sustained grade value as well as a maximum grade value for each grade parameter defined in the uphill and downhill tables, allowing for maximum conditions for grade to be considered as well as average.

Sustained Grade, Max Grade

Grades can now be entered as Sustained Grade and Max Grade. The Max Grade value must be equal to or greater than the Sustained Grade value.

When the max grade value is greater than the sustained grade, the maximum grade defines the maximum grade permitted whilst maintaining the sustained grade measured over the sample length.

If both the sustained grade and max grade values are the same then Quantm will handle the inputs as a maximum, that is, the sustained grade can go up to, but not exceed, that value for any location along the uphill or downhill sections of the alignment.

No Grade Break and Grade Break

Along with this a scenario can Use Grade Breaks that are defined in the Create New Project, Create New Scenario, or Duplicate Scenario windows. A check box, Use Grade Breaks, allows the user to switch them on or off.

Quantm will persist with the previous selection, that is, if you want to duplicate a scenario that does not have grade breaks, the check box will be cleared when duplicated. When creating a new project or a new scenario, whatever the selection was previously will be remembered and carried through.

No Grade Breaks

Scenarios without grade breaks set will allow you to define multiple grades to satisfy the need to build up catalog data files, but select only one active grade to be considered in the scenario. There are three inputs here that can be used, inputs for uphill and downhill are Sustained Grade (%), Max Grade

(%) and Sample Length (m). This is similar to how Quantm software handled grades before version 8 of the software was released.

For non-grade break scenarios, the corresponding grade length is a sample length, that is, a defined length that moves along the alignment for which the grade parameters need to be met. Think of it as a window the length of the defined Sample Length that moves along the alignment at each cross-section checking the sustained grade is being met within the window.

Therefore an alignment could climb or descend for an indefinite length so long as the sustained grade is being met within the Sample Length field. You can enter multiple grade entries in the table however only one entry, called the Active Grade, will be considered per geometry type. This allows you to build catalog files with multiple grade entries and refer to only the single grade entry that is relevant for their scenario/project. A blue tick is placed next to the Active Grade grade entry in the table indicating it is the grade to be used in the geometry type.

Note: To select the Active Grade, right-click on the desired grade entry in the table and then select Active Grade. Below is an example of the Grade tab when no grade breaks are used.

Grade Breaks

When the Use Grade Breaks option is selected upon creating a new project, a new scenario, or duplicating a scenario, the Grade tab in the Geometry Parameters changes. Grade break uphill and downhill parameters with corresponding maximum grade and minimum length fields are added to the UI.

Similar to non-grade break scenarios, multiple grade entries can be entered into the downhill and uphill tables. However unlike non-grade break scenarios where only one grade entry, or active grade, is considered, in grade break scenarios multiple grades can be considered.

For grade break scenarios the length is a critical length, that is, a maximum length at which the corresponding sustained grade can travel before a break in grade is required. Note a change of direction, that is, from uphill to downhill or vice versa is considered a grade break, as well as when a grade entry meets its critical length before flattening out. The image below is an example of a grade entry meeting its critical length before inserting grade breaks.

Quantm Grade Breaks come in three forms:

Below is an example of a grade break scenario. The first entry in the list is the condition with which the grade can travel for an infinite length without requiring a grade break. In essence sustained grades below this level are not considered a hill. Each subsequent entry in the grade table is then met as needed until the Upper Limit entry is reached. The Upper Limit grade defines the maximum grade condition that is to be used in the scenario. This is selected by right-clicking on the desired grade entry in the table and selecting Upper Limit. This places a dark blue tick next to the entry highlighting that it is the maximum grade parameter to be used in the geometry type.

A light blue tick is placed on all entries below the upper limit to show they will be considered in the scenario. The sections highlighted above are ignored.

Note: The Upper Limit does not need to be the largest or steepest value in the table. Any grade entry greater than or steeper than the selected upper limit will be ignored, hence they will have no ticks next to them. So in Figure 2 the downhill sustained grade entry of -8% and the uphill entries 6% and 8% are not considered.

Once the sustained grade and distance constraints have been met, the Grade Break conditions are used to force a break in the grade condition. One Grade Break parameter is specified for each geometry type and is defined by separate uphill and downhill maximum grade and minimum length conditions.

How a Grade Break is determined

During optimization: During optimization and the conversion between curvilinear and geometric, the system will try to insert grade breaks along the alignment at the length interval defined by the Upper Limit grade entry. For example, looking at the uphill grade entries in the second figure, the system will attempt to insert grade breaks along the alignment based on the critical length of 500m, which is the upper limit entry. It will also insert grade breaks at natural locations where the terrain permits and the grade break inputs; in this case; a maximum grade of +/-0.5% and a minimum length of 200 m are met.

In situations where the upper limit grade entry cannot be fitted, any flatter grade entries in the table will be considered. Otherwise, if there are no other grade entries a warning will be applied.

How Grade Breaks are reported

Grade Breaks are determined in the system by first identifying hills along the alignment. A hill is defined as being the area between two grade breaks. A grade break is defined as an area along the alignment where the grade does not exceed the Grade Break parameters, that is, it meets the grade break Max Grade and Min Length inputs.

The first stage in the process is to determine where along the alignment the upward hills exist. For example, to find all the hills that are heading upwards we start at the start of the alignment and travel along until we hit a grade break, then we find the start and end of that grade break (keeping in mind that the grade break may be longer than the specified minimum length input). It is then decided that the first upwards hill section is from the start of the alignment to the start of the first uphill grade break. We then move to the end of the first uphill grade break and continue along the alignment until we find the next grade break. This defines the second hill section, which is between the end of the first grade break and the start of the second grade break.

We then keep doing this process finding the areas of the alignment that are between the end of one grade break and the start of the next grade break. The process is then repeated looking for the hills that head downwards, as the grade breaks will not necessarily be in the same locations for both uphill and downhill sections of the alignment.

Once a hill has been found, we then find the appropriate row for its length in the appropriate downhill or uphill grade table (the first row whose critical length is larger than the length of the hill) and compare its average grade to the sustained grade allowed and its maximum grade to the maximum grade allowed. If it exceeds the allowed values a warning will be added to the alignment.

Essentially grade breaks are used to break a hill up into smaller sections that conform to the selected uphill/downhill grade parameters. Grade breaks themselves are normally low grade sections to allow vehicle breaks or engines to recover. Grade inflections are also considered grade breaks.

Below is an example of how the appropriate grade entry is reported against from a grade table of multiple grade entries. In this case, a downward hill has been identified between two grade breaks. The hill length is 600m and the average grade of the hill is -1.4%. Given the average grade of -1.4% is steeper than the -1.0% sustained grade entry and less than the -2.0% sustained grade entry, in addition to the hill length not exceeding the critical length of 600m, then the hill is reported against the -2.0% sustained grade entry.

Below is an example of a section of a hill that would be reported against an infinite critical length entry. In this case the upward hill section travels for a length longer than any defined critical length without inserting any grade breaks. For the sake of this example the length of the hill section is 10,000m and the average grade of the hill section is 0.4%. Given the average grade of 0.4% is flatter than the 1.0% sustained grade entry and the hill exceeds the largest critical length of 600m in the table, then the section of the hill would be reported against the 1.0% sustained grade entry and infinite critical length.

Note: If there are no grade breaks within a very flat alignment then the end points act as grade breaks defining a single hill from start to finish. This enables the Max Grade (%) for an infinite critical length entry to be steeper and considered against the sustained grade, i. e. the grade can peak at a max grade for certain lengths so long as the sustained grade is met.

Uphill and downhill grades

Uphill and downhill have separate areas to specify the grade ranges to be set within a geometry type.

Option Description

Grade (%) The grade range specifies the upper limit of the grade range to be considered.

Downhill grades are -ve while uphill grades are +ve.

Maximum

Exceptions

This value specifies the number of times the maximum desired grade can be exceeded up to the highest range specified in a set of results. A grade range higher than the desired needs to be specified for this value to have any effect.

(remove old images?)

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