4.5 Left Turns

This manual recommends that cycle facilities are re-established as on-road cycle lanes for the last 20 to 30m in advance of a significant left turn. The re-establishment zone provides time for vehicles and cyclists to observe each other and accommodate each other’s movements at the conflict point. This is as much to do with ensuring the safety of straight ahead cyclists as left turning cyclists.

Depending on the nature of the cycle facility along the main carriageway, a Vertical Transition will be required in the case of a cycle track to bring the facility to the main carriageway level. Equally, a Horizontal Transition, shifting cyclists to the right, may be required for an off-road cycle track or if there is kerbside parking or loading facilities in advance of a dedicated left lane or pocket.

The re-established cycle-lane must be continuous, clearly marked and legible so that vehicles weaving left across it know they must yield to cyclists who may be continuing straight ahead.



Re-Establishing from Off-Road Cycle Track to Cycle Lane

• Off road cyclists are re-established on the road well in advance of a junction
• Cyclists aligned so that they do not pop out in front of vehicles
• Transition curve radii allows cyclists to maintain speed
• Mandatory cycle lane, to prevent traffic encroachment
• Maximum on road exposure of cyclists = 30m in advance of junction
• Consider ASL (and / or box turn) to assist right hand turning cyclists (not shown)

Re-establishment requires that sufficient length is available and that the traffic environment is safe for cyclists, particularly in the case of Collector and Distributor roads.

Where the traffic environment precludes the use of a cycle lane, re-establishment can be achieved by means of a raised or similarly segregated cycle track.

Re-Establishing from Off-Road Cycle Track to Segregated Cycle Track

Principle of design

Right turning cyclists can weave across a single traffic lane to a feeder cycle lane before traffic starts to split into separate traffic streams.

• Used in vicinity of HGVs turning left
• Design re-establishes off road cyclists back on road in advance of junction
• Cyclists aligned so that they do not mix with vehicles
• Transition curve radii allows cyclists to maintain speed
• Segregated at grade cycle lane, to preclude traffic encroachment
• Design may require separate cycle signal stage (e.g. where turning HGVs are present), although not generally required
• Box turn required to assist right hand turning cyclists (not shown)

Cyclists passing on the inside of a traffic queue can frequently find themselves in conflict with right turning traffic coming from the opposing direction to turn into a side road.

This manual recommends that the cycle lane approaching the junction should be a minimum of 2.0m wide and that the cycle lane is continued through the junction and clearly marked. This will raise driver awareness of the potential for cyclists, improve the visibility of approaching cyclists and maximise the cyclist’s lateral evasion space in the event of a conflict.

Cyclists and Opposing Right Turning Traffic

• Wide (1.75 to 2.0m) red coloured cycle lanes provide additional legibility to all traffic (vehicles, cyclists) in congested junctions
• Wide cycle lanes provide some evasion space in circumstances of opposing traffic movements

On busier roads with higher vehicular capacity, multiple and/or dedicated lanes may be required for different movements.

This section looks at left-hand pockets (30.0m or less) and dedicated left-turning lanes (greater than 30.0m) in conjunction with the straight ahead movement. Dedicated right-turning lanes are dealt with below in Right Turns.

Where a single traffic lane with a kerbside cycle lane approaches a left turn, the straight ahead cycle lane should be continuous through the junction. Left turning motorists are expected to yield to any straight ahead cyclists before turning left.

Left Hand Lanes and Pockets

For left pockets and lanes, it is important that cyclists going straight ahead are re-established in their own intended alignment before introducing the turning pocket. Traffic can then turn into the left hand pocket across the cycle lane.

Left Hand Lanes and Pockets

• Put in left hand traffic pocket only if required (e.g. to run as a separately staged traffic movement, facilitate pedestrian crossing of side road, etc.)
• No ASLs – include box turns for right hand turning cyclists, as left hand pockets will (should) feature only at significant traffic junctions
• Keep signal cycle time short
• Limit pocket length to dimensions shown – otherwise cyclists in central cycle lane are overexposed between two lanes of moving traffic, and there is increased potential for faster traffic weaves into the left hand pocket
• Left hand pocket has no cycle lane – ensure pocket lane is suitable for cycling mixed with traffic, by keeping pocket length short, lane width tight (3m plus whatever needed for vehicle tracking)
• Not suitable where HGVs use left hand pocket
• Use reverse curves on footpath kerbs, reflecting more closely traffic movements, and improving drainage and litter management

Left Hand Pocket with Left Turning Cycle Lane

 

Left Hand Pocket

• Put in left hand traffic pocket only if required (e.g. to run as a separately staged traffic movement, facilitate pedestrian crossing of side road, etc.)
• No ASLs – include box turns for right hand turning cyclists, as left hand pockets will (should) feature only at significant traffic junctions
• Keep signal cycle time short
• Limit pocket length to dimensions shown – otherwise cyclists in central cycle lane are overexposed between two lanes of moving traffic, and there is increased potential for faster traffic weaves into the left hand pocket
• Left hand pocket has no cycle lane – ensure pocket lane is suitable for cycling mixed with traffic, by keeping pocket length short, lane width tight (3m plus whatever needed for vehicle tracking)
• Not suitable where HGVs use left hand pocket
• Use reverse curves on footpath kerbs, reflecting more closely traffic movements, and improving drainage and litter management

Left Hand Pocket with Left Turning Cycle Lane

• Put in left hand traffic pocket only if required (e.g. to run as a separately staged traffic movement, facilitate pedestrian crossing of side road, etc.)
• No ASLs – include box turns for right hand turning cyclists, as left hand pockets will (should) feature only at significant traffic junctions
• Keep signal cycle time short
• Limit pocket length to dimensions shown – otherwise cyclists in central cycle lane are overexposed between two lanes of moving traffic, and there is increased potential for faster traffic weaves into the left hand pocket
• Use reverse curves on footpath kerbs, reflecting more closely traffic movements, and improving drainage and litter management

Streaming of cyclists between the left turning and straight ahead traffic lanes is not recommended for distances greater then 30.0m. Where the left turning traffic longer than this is required, the cyclist should be brought to the junction on a kerbside cycle track. The junction should be signalised and cyclists provided with their own stage.

Bus Lanes and Left-hand Pockets and Dedicated Left-turning Lanes

Where a bus lane exists, with a shared or adjacent cycle lane, there is a need to safeguard priority for both buses and cyclists travelling straight through the junction.

The layout below provides for cyclists and buses to continue straight ahead in a shared lane, but traffic moving from the general traffic lane must cross the bus/cycle lane to access the left-turn pocket.

Bus Lanes and Left-hand Pockets and Dedicated Left-turning Lanes

• Bus lane and cycle lane brought to stop line
• Left turn vehicles required to cross bus lane and cycle lane to enter left hand pocket
• Put in left hand traffic pocket only if required (e.g. to run as a separately staged traffic movement, facilitate pedestrian crossing of side road, etc.).
• No ASLs – include box turns for right hand turning cyclists, as left hand pockets will (should) feature only at significant traffic junctions
• Keep signal cycle time short
• Limit pocket length to dimensions shown – otherwise there is increased potential for faster traffic weaves into the left hand pocket
• Use reverse curves on footpath kerbs, reflecting more closely traffic movements, and improving drainage and litter management

Shifting the Cyclist Right

Where a dedicated left-turn lane is to be provided or where there is kerbside parking or loading in advance of the junction, the challenge is to shift cyclists (who are going straight ahead) to the right of the left-turning traffic, without being hit by traffic from behind.

Cyclists should be shifted to the right only under the protection of a physical island. The left turn pocket can be introduced downstream of the island. The geometry of the entrance to the left turn pocket should require “turning” rather than “veering” in order to ensure slow vehicular speed.

Shifting the Cyclist Right

• Used to re-establish off road cyclists back on road  in advance of minor junction
• Cyclists aligned so that they do not pop out in front of vehicles
• Transition curve radii maintain cyclists speed
• Mandatory cycle lane, to prevent traffic encroachment
• Maximum on road exposure of cyclists = 30m in advance of junction
• Keep footpath build out clear, to improve legibility

Subject to Department Approval – Refer to Traffic Signs Manual

There can be a conflict between pedestrians crossing side roads and significant volumes of left turning traffic. In some urban situations, the solution has been to simply omit the pedestrian crossing.

This manual proposes a solution as follows, subject to Department approval, whereby the pedestrian facility can be provided. This will not be suitable where large vehicles (trucks / buses) are turning left.

Late Release Signalisation

Stage 1 Pedestrian Crossing Stage
Side Road:  Green man
Main road:  Red left turn traffic filter and green straight-ahead filter

Stage 2 Early Transition Stage
Side Road:  Green man so those crossing may continue to do so
Main road:  Flashing amber filter for left turning traffic commences and green straight-ahead filter

Stage 3 Transition Stage
Side Road:  Amber man
Main Road:  Flashing amber for left turning traffic and green straight-ahead filter

Stage 4 Left Turning Traffic Stage
Side Road: Red man
Main Road: Amber left filter and green straight-ahead filter

Stage 5 All Red Stage
Side Road: Red man
Main Road: Red left filter and red straight-ahead filter

Left curve radius is too generous

The problem of kerbside cyclists being cut out by a turning vehicle is universal. When that vehicle is a large vehicle, the issue becomes critical.

Difficulties with Dedicated Slip Lanes

Conflicts between the large turning vehicles and cyclists / pedestrians on left slip lanes present a significant risk. Slip lanes often give drivers an unreasonable sense of priority, and by virtue of their oblique geometry, they restrict views of cyclists and pedestrians. They should be removed wherever possible.

A segregated cycle lane along the main road that clearly continues across the mount of the side road is a much safer solution for cyclists.

If a slip lane must be maintained, the arrangement shown below in Modifying Existing Left Hand Pockets.

How The Principles of Sustainable Safety Apply

The most relevant principles of Sustainable Safety are Legibility, Homogeneity, Functionality, and Forgivingness. Designers should consider these principles in generating junction solutions. Considering each in turn:

Left hand pockets should be removed wherever possible. A simple solution is to re-assign the existing pocket as footpath, verge or parking so that the cyclist has the correct alignment.

Where a left turning pocket cannot be removed, the layout can be modified to either shift cyclists to the right in advance of the pocket, or to enhance the level of protection for cyclists.

Shifting Cyclists to the Right

If significant volumes of left-turning traffic preclude the removal of an existing left turning pocket, the kerb should be re-aligned to shift cyclists to the right as shown below.

Shifting Cyclists to the Right

• Cyclist is brought to the correct alignment in advance of the pocket with a physical build out.
• Short section, 30m max, of existing left pocket retained in advance of junction.

Enhanced Protection at Existing Left Hand Pockets

Where an existing left hand pocket needs to be retained, cyclist safety can be improved by adopting the details shown on the following drawing.

Modifying Existing Left Hand Pockets

• Segregating the cyclist as close as possible to the (blue) conflict point, to prevent large vehicles from cutting across;
• Providing a cycle track (as opposed to lane) in the left turn pocket;
• Increasing the left turn radius to allow for tracking of large vehicles;
• Including raised bollards etc. at the end of the left hand cycle track, and at the start of side road cycle track, to keep vehicle from encroaching on cyclist’ space while turning left.