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urban planning

Case study: the problems of Coppins Crossing

Coppins Crossing Road is currently a low-level crossing over the Molonglo River. Active travellers are hit the hardest when direct routes are lacking.

Road design has evolved to put great emphasis on road safety. Many of the road safety terms are for design features and considerations that impact on road safety, particularly vulnerable road users.

The Coppins Crossing is a river level crossing on the Molonglo River. The last section of the Coppins Crossing Road is sandwiched between the north and south sections of the John Gorton Drive duplication but the section around the river crossing remains and will be replaced with a bridge in 2024. The bridge is part of the 1.5km John Gorton Drive 3C Extension (JGD3C). The Coppins Crossing Road descends from the north side 36m into the valley to a level crossing and then ascends again to meet up with the south section of the John Gorton Drive.

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Considerations discussed here:

  1. Gradient 
  2. Road Reserve and cutting
  3. Exposure length
  4. Marked shoulder
  5. Bike lane
  6. Country road grade
  7. Road maintenance

Gradient

The cycle path design for the ACT is described in the Active Travel Facilities Design – Municipal Infrastructure Standards 05 (MIS05) document and cites the Austroads standard Guide to Road Design Part 6A: Paths for Walking and Cycling 2017 (AGRD06A). 

“4.4.1 Path designEstate Development and RetrofitPath design is to consider land use and route hierarchy contexts. For example, a trunk path on a Main Community Route through a green corridor in a suburban context will have a higher design speed than a trunk path on Local Community Route in an inner urban context. Path design will comply with AGRD06A, references to the relevant sections of AGRD06A are shown in brackets:

> Width (AGRD06A Section 5.1)

> Bicycle operating speeds (AGRD06A Section 5.2)

> Horizontal curvature (AGRD06A Section 5.3)

> Path gradients (AGRD06A Section 5.4)

> Clearances and the need for fences (AGRD06A Section 5.5)

> Crossfall and drainage (AGRD06A Section 5.6)

> Sight distance (AGRD06A Section 5.7

)> Changes in level (AGRD06A Section 5.8)

> Surface treatments and tolerances (AGRD06A Section 5.9 and 5.10)

> Lighting and underground services (AGRD06A Section 5.11 and 5.12)”

Active Travel Facilities Design – Municipal Infrastructure Standards 05 (ACT Government, April 2019), page 41

The Austroads AGRD06A standard includes recommendations for uphill gradients for cyclists. From figure 1 below the “desirable uphill gradients for ease of cycling” depend on the duration of the climb. E.g. For a 5% gradient, the “desirable” length of the gradient is no more than 80m.

Figure 1: Desirable uphill gradients for ease of cycling, AGRD06A, page 34

The conditions found for the cyclist at the Coppins Crossing considerably exceed this. Figure 2 shows the gradient profile along John Gorton Drive. Gradients are displayed on a colour scale, from a climb of +25% to a descent of -25%. The steepest climbs are in dark red and the colours span the rainbow to the steepest descent in dark blue. 

Figure 2: Whitlam to Coombs gradient profile, John Gorton Drive

The gradients of the road between Whitlam to Coombs along John Gorton Drive can be as great as 10%. The histogram shows that on the south side of Coppins Crossing there is a section close to 10% for a length of approximately 180m and a gradient of 9% on the north side for a length of 100m. Gradients above 5% are common. The circumstance at Coppins Crossing is not compliant with the Austroads AGRD06A standard. 

Figure 3: Histogram of gradients between Whitlam to Coombs along John Gorton Drive

Road Reserve and cutting

“Road reserve – Land comprising the road and verge. And also referred to as the road or street corridor in this Standard.”

Active Travel Facilities Design – Municipal Infrastructure Standards 05 (ACT Government, April 2019)

The Coppins Crossing Road is very narrow and steep either side of the river-level crossing. The road is cut through the side of the valley to reduce the gradient. The cutting is just wide enough for two way traffic. The road reserve provides no verge for the cyclist to leave the road, such as in an emergency. 

Marked shoulder

“Marked shoulder – Refers to the sealed edge of roads outside of the travelled carriageway defined by an edge line (the shoulder) where cyclists are legally allowed to travel. This facility is almost invariably associated with unkerbed roads and is often used on rural roads.”

Active Travel Facilities Design – Municipal Infrastructure Standards 05 (ACT Government, April 2019)

Much of the on-road cycling in the ACT is done on the marked shoulder of the road as it provides some segregation from the road traffic. Coppings Crossing Road is lacking even a marked shoulder on much of its length. 

Bicycle lane

“Bicycle lane – A special-purpose on-road traffic lane for the exclusive use of cyclists marked in accordance with Australian Road Rule 153 and as described in AS1742.9 and AGRD03 Section 4.6.7. Bicycle lanes may be of varying widths depending on the road speed environment and their use is defined by the Australian Road Rules for cyclists and other road users.”

Active Travel Facilities Design – Municipal Infrastructure Standards 05 (ACT Government, April 2019)

The Coppins Crossing Road does not have a bicycle lane and none is planned. 

Exposure length

“Exposure length – The length of a bicycle lane, typically at a slip lane, in which the cyclist can be regarded as having a high risk of conflict with vehicular traffic.”

Active Travel Facilities Design – Municipal Infrastructure Standards 05 (ACT Government, April 2019)

Exposure length is a useful concept as Coppings Crossing Road is steep, narrow, without marked shoulder and bicycle lane, and the cyclist can be regarded as very vulnerable. Steep and narrow is a bad combination as the cyclist is then unsteady and slow. At low speeds, the time spent in the exposure length is greater, thereby increasing the risk. On steeper grades, cars have higher speeds and less control. The cutting means for the cyclist there is no escape. Particularly the south side of Coppings Crossing is very dangerous. 

Rural road standard

Some roads are very old and were built in a way that would not comply with modern road standards. In the ACT rural roads are often sealed old roads that predate Canberra’s urbanisation. Many of these roads have been upgraded but some still survive, including Coppins Crossing Road. The extreme ends of the Coppins Crossing Road have been upgraded as a result of the John Gorton Drive duplication but the section around the river crossing remains to be replaced with a bridge. The bridge is part of the John Gorton Drive 3C Extension (JGD3C). Coppings Crossing Road, as a rural road, has neither a marked shoulder or a bicycle lane. The road reserve is narrow and dangerous. The RiotACT reported roads built to rural road standards are “only suitable for low volumes of traffic” (see quote below). As a north-south corridor and part of the Molonglo development, the traffic volumes along Coppins Crossing Road can be expected to be high.

“Detailed designs will also be prepared in coming months to upgrade Morisset Road in Mitchell to support future development in the area. Morisset Road is currently 1.25 kilometres long and built to rural road standards, meaning it is only suitable for low volumes of traffic.”

Government to duplicate 4.5 kilometres of William Hovell Drive, Lachlan Roberts, 19 September 2019, The RiotACT

Road maintenance

As a result of the John Gorton Drive 3C Extension, road maintenance of the Coppings Crossing Road seems to have been discontinued. Road edges are breaking away, the road is uneven and potholes are forming. The narrow and windy road is a hazard to both motorists and cyclists that share the road.

Conclusion

There is a primary school in Coombs. Whitlam and Coombs are part of the same development. One could consider the scenario of a child riding from Whitlam to the Coombs primary school. This is a distance from Whitlam to the Coombs primary school is 6.4km, compared with only 4km to two primary schools in South Belconnen (Weetangera and Macquarie). Considering the nature of the Coppins Crossing discussed here and the greater distance from Whitlam, the two primary schools in South Belconnen are a better alternative.  The ACT Government must regard the Coppins Crossing road as unsafe by its own road standards. Even adults and experienced cyclists are ill-advised to ride there.

Coppins Crossing Road from Pipe Flat, Molonglo Valley
Coppins Crossing Road from Pipe Flat, Molonglo Valley

8 replies on “Case study: the problems of Coppins Crossing”

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