Design Rule Purpose
One of the most important aspects of good design of linear assets is to make sure that they avoid all obstacles and follow an optimal path. Optioneer can facilitate this process by taking constraints and their importance into account. The objective find a path which minimises traversing constraints as far as possible.
How to Configure
This design rule requires the following inputs:
Please refer to Geospatial Data in Optioneer Fundamentals.
Hard Constraints (no-go zones)
Hard constraints are areas which should be avoided at all cost. These are defined by selecting which data layers are hard constraints.
Hard constraints can't be crossed and if the route goes through a hard constraint, it is considered infeasible. In situations where no route avoiding all hard constraints can be found, Optioneer will try and minimize the length through the hard constraints in the first instance.
Soft Constraints and their Weighting
Soft constraints are areas that should be avoided if possible. These are defined by selecting which data layers are soft constraints and assigning them a penalty. We recommend using the scoring system below.
Soft constraints can be crossed but there is a penalty or a cost associated with doing so. The objective of Optioneer is to minimize the total penalty of the route option.
In the example below, residential and functional buildings were set as hard constraints (i.e. should be avoided at all costs). Other layers were set as soft constraints.
The four alignments can be compared on the basis of constraints only (i.e. no other aspect taken into account).
The routes are mostly going through constraint-free areas, but there are a couple of sections which do go through constraint areas (see explanation below).
All routes share the first section and as such, there is no difference between the routes there. The only differences appear in the second section. Looking at the second section, we can see that:
the purple route is an alternative which cuts through a long distance of woodland and with a small section going through water. This route will have the highest penalty score due to traversing constraints.
the red and cyan routes diverge in the middle section but neither of them goes through any constraints. These options will have an equal penalty score due to traversing constraints
the blue route is longer and doesn't look as intuitive to designers' eye but it cuts through less woodland area towards the end and therefore will have the lowest penalty score due to traversing constraints.
Optioneer will evaluate many other parameters to help the user assess the route. So whilst penalty scores can provide valuable insight, they are just one of the tools used to analyses routes.
Ensure that only absolutely critical hard constraints are designated as such. Too many hard constraints will lead to skewed results. Optioneer will struggle to find a feasible solution as everything would look 'bad'.
All soft constraint scores / weights for a given config should be relative to one another. It is good to come up with a scoring system. We recommend using the table in the 'How to Configure Section', but other examples include:
Red-Amber-Green converted into points, like Red = 5 points, Amber = 2 points and Green = 0 points (green constraint is not really a constraint!)
0-4 point scoring scale - which is a five-step scale, with 0 indicating a 'neutral' area to go through and 4 indicating a highly unfavourable constraint
0-10 point scoring scale, similar to 0-4 point
real cost of land acquisition expressed in GBP or USD - here 0 would often indicate a public right-of-way and then costs of land might be sourced from a database or a survey.
Optioneer will only consider preference based on the point / scoring system which means that if two layers carry the same penalty, they would be treated the same. It is important to come up with a coherent methodology for assigning values to constraints.
Optioneer will only report going through areas that do carry a penalty or cost. If the value is set to 0, Optioneer will ignore it and not report this value on the Vertical Profile chart.
Input & Output Summary
This design rule requires the 'Constraints' and 'Environment' dataset.
Penalty / cost values for soft constraints
List of hard constraints
Configuration of penalty layers under Model/Routing Constraints- Penalty Scores & Routing Constraints- Penalty Scores:
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Total path cost due to constraints
Total path length through [layer]
Layers crossed at every point of the route
plot on the vertical chart
Summary of layers crossed on the Vertical Profile Chart under Composition/ Penalty:
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