The need for choice

There is no single best alignment.

Planning is subjective, and many issues are contentious. What value can be placed on ensuring that a freeway is kept out of sight of a scenic lookout? What is the social cost of land acquisition? The cost of an alignment intruding into private properties is not a simple function of the extent of the intrusion; extraneous (and frequently unquantifiable) costs such as legal proceedings, public relations, and delays have to be considered.

A calculation of the difference in construction costs between an alignment that intrudes and one that does not has to include these subjective factors when determining whether the intrusion is worth considering.

As an alternative, you can use the Quantm system to produce a selection of low-cost alignments that meet the objective criteria, and then allow planners (or the community) to select the alignment which represents the optimal balance between low-cost and, in their opinion, minimal adverse impacts. You can also customize that alignment if necessary.

For there to be a choice, meaningful differences between the alignments must be produced. For instance, if you took the least cost-compliant alignment and moved one intersection point 1 mm, none of the many intervening alignments could be considered a real alternative to the first. The optimization process of Quantm ensures that the selection of low-cost alignments presented to the planner contains a range of genuine alternatives, rather than minor variations of a single least-cost solution.

The difference between planning and design

Typically, planning repeats a number of key questions until the answers remain unchanged. For transport infrastructure, questions may include:

• Is a road/railway that connects towns A and B necessary or desirable?

• What capacity and/or standard should it be?

• What route should it take?

• What will it cost?

• How much CO2 will be produced from construction and future traffic?

Since information regarding the costs may change throughout this process, (a), (b), and (c) may be repeated to incorporate new information. This may lead to different decisions, requiring a full or partial reassessment as well as another iteration of the questions.

Planning determines where the route should be located and obtains preliminary estimates of the cost: Design defines the details that allow the route to be constructed and provides more accurate cost estimates.

Planning is where macro impacts can be identified and assessed: Design is where any micro effects can be evaluated.

The difference between planning and design affects how details are viewed. The planner is concerned with the big picture and the designer with the detail. An alignment that is good from a planner’s perspective will be deficient from a designer’s if the alignment fails to address critical details. The purpose of the Quantm system is to produce superior planning alignments for the designer to use as a starting point for design.