Directness

A cycle highway route that is more direct allows the user to get from A to B faster and with less effort. Direct route increases the outreach of cycle highway: the shorter the route, the more likely is the potential user to choose bicycle for daily commuting.  
 

How to measure directness?

Directness can be measured in terms of detour factor: the length of the route (Lch) divided by the distance as the crow flies (Lo).

Detour factor = Lch/Lo

As one of the cycle highway goals is creating an attractive alternative to car trips, directness can also be considered in comparison to the car route (Lcar). Cycle highway should offer more direct connection than the route for cars:

Lch < Lcar

Why is it important?

A more direct route reduces time and effort necessary to get from A to B. Therefore cycling is more competitive and people are more likely to choose bicycle for daily journeys. 

On network level, the benefits are not linear, but grow quadratically – routes that are 20% more direct mean cyclists can reach targets in area 44% bigger. Why? Area is proportional to the square of radius, so assuming one is willing to cycle e.g. 12 km one-way:

• If you have ideally direct routes to all your targets, you can reach targets in radius of 12 km and area of 452 km²;
• If the cycling routes require making 20% extra distance (detour factor 1.2), with the same effort and time budget you can reach targets in radius 10 km and area of 314 km². 

Of course, ideally direct routes are rare in the real world, but the same proportions hold for different numbers as well (e.g. detour factor 1.125 vs 1.350, 1.25 vs 1.5 etc.)

How is it related to other criteria?

As a side effect, direct route is usually cheaper to maintain: if the route is shorter, there are less signs to renew, less snow to clear in winter, less energy is needed to light the route etc. Directness can also contribute to route readability – a clear straightforward direction means you are able to quickly understand and follow the connection and are more able to orientate yourself.

Compromises might be made for example to increase the route connectivity (pass near another town, concentration of workplaces, important public transport hub), attractivity (f.i. through a more beautiful or less monotonous landscape) or to avoid steep slopes or conflicts with cars. Sometimes the most direct route would be extremely costly to construct (for example a bridge across a lake or a tunnel through the mountain).

Reducing the travel time can be achieved also by good design speed and reducing the number of interruptions, e.g. giving priority to cyclists on crossings or providing grade separated crossings. 

How to make a direct route?

Directness is mostly decided during the phase of route planning, when different route options are investigated. Following another linear infrastructure (e.g. railroad, motorway, canal etc.) can result in a very direct route. However, it is often possible to provide shortcuts also at the design phase, e.g. by:

• strategically located tunnels and bridges providing new shortcuts;
• filtered permeability – enabling cyclists to continue through a street while keeping it a dead end for cars.