Gradients are hard to guess. We do not have an eye for it. Riding a bike, we notice when it gets too steep, however, it is hard to say how steep that is. That is what the gradient measures.
Often a steep section of 30 m is all that is required to bring us to a stop. The bike could be pushed that distance, but it is not very likely that a cyclist would want to push the bike up a hill. What we would like is that the paths are never so steep that we come to a stop. That is going to take careful path design in hilly terrain.
What is unrideable?
When a hill becomes unrideable depends on your fitness and the gearing of the bike. Mountain bikes have much lower gearing, as they are designed for riders that spend a lot of time grinding up hills. Road cyclists tend to use the momentum in undulating terrain to get over hills. The roll resistance of a road bike is low, and they are designed to go straight and fast. The gears are set a lot higher to pedal against the wind resistance at speed. A cyclist’s fitness and strength make a big difference, too. The young and fit are in an enviable position, but for most of the population their fitness and strength will only be moderate.
Austroads is the Australian design standards body for the transport infrastructure that we find in our cities including roads, footpaths, and bicycle paths. In most states, roads, footpaths and bicycle paths are three different things. The ACT is unusual in that we have community paths which are shared with cyclists and pedestrians. These community paths are shared with wheeled mobility devices such as scooters. Canberra’s community paths are getting increasingly – and sometimes dangerously – busy.
What makes a good path?
Austroads standards for path design will be covered in another article. The pathwidth, surface smoothness and gradient are of importance.
For two bikes to pass at speed the paths need to be wide enough to provide room for error. This is typically 0.5 to 1 m, depending on how busy the paths and how wide the handlebars are. The paths need clearance to obstacles adjacent to the path such as trees and post of a similar distance. Two cyclists colliding head-on, travelling at 25 km/h can be seriously hurt.
At speed small deviations in the surface of the path due to cracking or roots will cause the cyclist to be thrown off balance and possibly lose control. On two-way paths that are common in Canberra this could lead to a head-on collision. Smooth and clean surfaces are also important for traction, which is essential for steering and braking. The chances of an accident increase when the path is slippery, dirty or bumpy.
The Austroads recommendations for gradients are to keep bike paths less than 5%. This is important for going both up and downhills. Inexperienced riders have trouble controlling their bike and may crash due to difficulties with braking. This is not because the bike has poor brakes, but rather the rider does not have sufficient coordination and/or judgement to negotiate a steep and windy path. The ride may veer into the path of an oncoming cyclist and/or pedestrian or off the path entirely. Community paths are a shared path environment and safety depends entirely on the ability of a cyclist to suddenly stop. This is much more difficult on steep paths.
Measuring a gradient is not so easy. To measure the gradient over 30 m, it is necessary not only to have an accurate measure of the distance but also the vertical elevation change.
In development applications, the gradients of the roads are provided, but this is an exception. Generally, the ACT Government does not provide information about the gradients of the roads and paths.
Digital Elevation Models are terrain maps that are generated from various sources, including satellites. The advance of these models is considerable. They cannot distinguish between ground and tree canopies. The best freely available Digital Elevation Models are now accurate to 5 metres. With this level of uncertainty, they provide a good estimate of the elevation rise of a bike path over a kilometre or more in length. This will let us calculate the average gradient but not the maximum gradient or gradient for a path segment of only 50 m.
A more precise measure of gradient available to the cyclist is provided by the data from cycle computers. Cycle computer from Garmin and Wahoo have air pressure sensors built-in, and can register small variations in altitude of just a few metres. This allows the Wahoo device to provide gradient estimates in real-time every few seconds. Should the climb gradient be consistent this could provide a quite accurate measure. However, the paths in Canberra often dip and weave and this results in the measure bobbing like the reading on a bathroom scale. Still, with online analysis, such as on the website Velo Viewer, the data from cycle computers can provide invaluable information on the terrain.
The ACT Government has a Digital Elevation Model of the ACT urban area with one-meter contours. This information is available through ACTmapi, which the ACT Government uses for urban planning and municipal services. Public access to this data is limited. ACTmapi also includes older paths but is not quickly updated, so that it provides little insight into new suburbs where the paths are new and the terrain may have changed. ACTmapi is not especially useful for estimating gradients in new areas of Canberra.
It is worth mentioning that modern surveying techniques can measure heights and distances down to the millimetre. This equipment is expensive and not generally available to a cyclist. It certainly cannot be used on the move. Such devices remain the tools of the construction industry.
Riding out of the Molonglo Valley
Riding south across the Molonglo Valley to the Belconnen valley, the three likely crossing points are: Aranda hill on CBR Cycle Route C5 (639 m), Coulter Drive (655 m), or William Hovell Drive by Higgins (642 m). The John Gorton Drive Bridge deck will be 24 m above river level, and the climb to the top of the ridge from the bridge will be around 106 to 119 m depending on the route. This is not too much in itself. With a gradient of just 5%, the bike path to the Belconnen ridge would only be 2.1 km long, with an optimal corridor.
Route along John Gorton Drive
The John Gorton Drive Bridge, when it will be finished in 2025, will be essentially flat. Heading north, the section of John Gorton Drive to the Sculthorpe Avenue intersection will need to be around 5% for it to be suitable for the later construction of the light rail (ITP). The light rail corridor requires a maximum gradient of 4.5 %, however, short sections can exceed that up to 8%. After the Sculthorpe Avenue intersection, the gradient on John Gorton Drive increases to about 12.5%.
A Main Community Route is planned on either side of the John Gorton Drive dual lane carriageway. This path to Coulter Drive may be too steep for most cyclists without an electric bike.
Route along Sculthorpe Avenue
The intersection of Coulter Drive and William Hovell Drive can be reached by an alternate route through the suburb of Whitlam. Sculthorpe Avenue is the main road (major collector) through Whitlam and sweeps through the valley formed by Deep Creek. From the development applications for Whitlam Stages 2 and 3, Sculthorpe Avenue has a maximum gradient of 8% (less than John Gorton Drive). In Whitlam Stage 1, a local community route (LCR) branches of Sculthorpe Avenue along McDonagh Crescent of a moderate gradient to the Coulter Drive and William Hovell Drive intersection. The maximum gradient on this route would be about 8%.
A comparison with the new suburb of Macnamara, a Ginninderry estate, is useful. The gradient of the main community route in Whitlam is significantly steeper (8%) than the main community route in Macnamara (maximum gradient 5%). Both Macnamara and Whitlam are in the Molonglo Corridor, however, it would seem the area around Whitlam less favourable.
Route to Bindubi Street
The route to Belconnen via Bindubi Street (CBR Cycle Route C5 up Aranda hill) would follow the future light rail corridor through Molonglo 3 East. The estate plan for this area is yet to be released. Further information should be available in 2021. However, the Molonglo 3 Stage 2 Proof of Concept report by Roberts Day (March 2019) would indicate that the “transit boulevard” follows the flat valley of Coppins Creek to join Bindubi Street. A community cycling route is planned along this boulevard.
Route to Higgins
The final mystery will be the route west to Higgins. The William Hovell Drive will be duplicated and this should include a community path. William Hovell Drive climbs steeply to the ridge and I would expect the cycleway to be built parallel to the road. This simple design will impede cyclists, unfortunately. Should the goal be to ride to Higgins, following John Gorton Drive to the William Hovell Drive intersection is a dogleg (6.2 km, 133 m climb, 45 m descent).
A better route to Higgins would be through Whitlam Stage 4. The development application for this area is yet to be released. In principle, however, there is space in the Kama protection zone for the path and space for possible switchbacks above the Deep Creek dam. It would be worth considering what can be done to realise this route while there is still time.