1.7 Integration and Segregation

The three principles of sustainable safety relevant to integration are functionality, homogeneity and legibility.

Functionality

In an integrated environment, pedestrian and cycle movements, loading and public transport facilities etc, are prominent functions. Integrated cycling is appropriate in these cases as the through traffic function is subordinate to, equal to, or limited by, other road and street functions. Environmental and amenity objectives etc may also apply.

Homogeneity

The graph below recommends the traffic volumes and speeds at which integrated cycling is the optimal solution. The design should include controls such that the appropriate speeds and volumes are met, thereby creating an attractive and safe integrated cycling environment.

Legibility

It is important that the low speed environment is self-evident, self-enforcing and self-explanatory, regardless of the number of cyclists, time of day etc.

Notes on Distributor Roads

• Integrated cycling is generally not recommended for primary distributor roads whose function is the optimal movement of through vehicular traffic.
• It is recognised that integration, e.g. cycling in bus lanes, may feature on certain distributor roads, particularly in locations where there is no possibility of providing segregated facilities. Careful attention is required to the traffic speed, mix and turning movements in these locations.

A high Quality of Service can be achieved in a well designed integrated environment.

Many residential and access streets already offer a high quality of service to cycling. Cycling two-abreast on quiet, interesting, well-surfaced streets and roads can be attractive to cyclists. In many cases there is no physical infrastructure involved, other than the self-evident and self enforcing nature of the environment.

Heavy congestion and high traffic volumes will limit Quality of Service.

The three principles of sustainable safety relevant to segregation are functionality, homogeneity and legibility.

Functionality

If the primary function of a road in a Sustainable Urban Traffic Plan is for motorised traffic, (e.g. urban distributor road, high volume / mass transit sustainable travel routes such as QBC and BRT) this function may be compromised or undermined through the introduction of an integrated cycling facility and, in turn, discourage users from adopting sustainable travel modes.

See also, Principles Underpinning Development of the Quality Bus Network and Cycling, October 2009, Department of Transport.

Smarter Travel – The existence of current heavy traffic volumes does not automatically presume that cyclists should be segregated. It may be that such volumes are not in keeping with a Sustainable Urban Traffic Plan, and reductions in traffic speed and volume is required in any case.

Homogeneity

The graph below recommends the traffic volumes and speeds at which segregated cycling is the optimal solution.

Legibility

It is important that the environment is self-evident, self-enforcing and self-explanatory. In order for this to be achieved segregated tracks should:

• Discourage obstruction e.g. wheelie bins etc
• Clearly identify access, egress, priority and direction of cycling
• Commence and terminate with smooth transitions

• Drainage: Additional drainage may be required for segregated facilities
• Maintenance: It is imperative that segregated facilities are kept free of debris and litter, and have robust, high quality surfaces.
• Frequency of Junctions: Frequent side roads will interrupt the benefit of a dedicated facility. In such cases, traffic speed and volume control in conjunction with integrated cycling may be a better option
• Minor junctions (access streets, entrances etc.): It is important that traffic turning across off road segregated facilities is made fully aware of the possibility of cyclists on the facility, have adequate sight lines, and turn at an appropriate slow speed.
• Road Works: If cycle track is closed due to road works, a segregated alternative should be considered.
• Enforcement: Should be considered if intended design is compromised by other road users
• Driveways: See entrances for detailing of cycle priority past entrances and driveways
• Pedestrians: It is important to assess the likely pedestrian activity and conflict points at key points along the route, the consequential requirement for cyclists to yield priority, and the potential impact on cycling QOS if priority is frequently lost to pedestrians

Subject to a quality design and maintenance programme, segregation can offer

• Improved reliability and predictability of the route
• High levels of comfort, including noise levels, air quality and stress factors
• Encouragement to novice, risk-averse and prospective cyclists to cycle more regularly – an overriding ambition of the National Cycle Policy Framework

1. Choose your preferred cycle environment
   
   Choose the type of facility you would like to have (e.g. mixed streets), and then reduce the speeds and volumes of traffic to an appropriate level. This approach is appropriate when the designer’s intention is to emphasise an informal, calmed, relaxed town or village centre, or perhaps where the road is so narrow that there is no possibility of dedicating space to cycling.
2. Plan your traffic speeds and volumes:
   
   Determine the design speeds and volumes of traffic according to the regional and/ or local sustainable traffic plan, and provide the appropriate cycling facility for that regime.

The guiding thresholds in this graphic represent the most widely internationally-accepted values of traffic speed and volume for various cycle provision options. They are approximate values in their scope, to give designers a sense of the appropriateness of their design solutions.

It behoves the designer to ensure that the Principles of Sustainable Safety, especially, Functionality, Homogeneity and Legibility, are applied to each design, regardless of the solution(s) offered in this graphic.

The graph’s Y-axis is the total two-way vehicular flow per day based on AADT. Some useful rules of thumb:

1. Peak hour traffic volumes = approximately 10% of 24-hour AADT
2. Peak hour traffic splits 66% inbound 33% outbound
3. A bus or HGV is equivalent to 3 PCUs (passenger car units). A busy bus lane (e.g. a bus every minute, and regular taxies) could have as high a traffic flow (in PCUs) as the next traffic lane.
4. A busy inbound urban  traffic lane within a signalised system carries between 650 – 850 PCUs per hour.

In cycle design, it is not the theoretical speed of traffic, or the posted traffic speed limit – it is the actual 85%ile traffic speed that counts

The actual speed of traffic can be quite different to the signed speed limit for the road, especially off-peak. In some cases, the roadspace may need to be re-configured to ensure that speeds of traffic are no higher than the designer intends within the design.

Traffic lane widths are an important consideration. With the exception of primary distributor roads, traffic lane widths should not exceed 3m in general.  (see Traffic Management Guidelines, Table 9.2: “Typical Lane Widths”.  ).

Further guidance on Speed and Traffic Calming can be found in the Traffic Management Guidelines, Chapter 6, Table 6.1(b) “Traffic Calming on Existing Roads”.

Average urban commuter cycling speeds are up to 20 km/h.  Where weaving occurs, the Dutch advice (CROW) is to limit the speed differential between bicycle and traffic to 10km/h, in order that bicycles can weave in front of vehicles with relative comfort and safety etc.

For this reason, the 30km/h speed limit (ensuring it is observed) becomes central to the concept of mixed traffic.

Beyond 50 km/h actual speed, the relative speed of vehicles to cyclist is getting high (30 km/h or higher). In relative terms, cyclists travelling at 20 km/h in a 50 km/ h zone are equivalent to pedestrians walking along the road with their backs to traffic, within a 30 km/h zone.

For this reason segregation is generally appropriate for urban roads where:

• actual motorised speeds are above 50km/h or
• on such roads where the speed limit is set at 60 km//h or higher

In reviewing the graph, the threshold of 10,000 AADT is important. At 30 km/h actual traffic speed, this represents the maximum level of traffic flow at which mixed cycling is likely to be the most appropriate choice. 10,000 AADT is roughly equivalent to 1000 PCUs in the peak hour, or 666 PCUs inbound in the morning peak hour.

At 50km/h actual speed (the standard urban speed limit) the maximum traffic flow is 5,500 AADT if mixed cycling is preferred. This is equivalent to 360 PCUs inbound in the peak hour – a relatively low volume of traffic.

In general, and under the Principle of Legibility, this manual does not recommend designs that intend cyclists to slew across multiple lanes of traffic for right turns.

While some experienced cyclists may negotiate such manoeuvres, where possible, the designer should provide an appropriate crossing arrangement in accordance with the Principles of sustainable safety.

If the street or road in question has more than one general lane per direction (between junctions), the designer should re-assess the layout:

1. If the road is genuinely and necessarily a higher order collector / distributor road with a strong vehicular traffic function, cycle lanes or tracks are likely to be required
2. If the road has low amounts of through traffic, the roadspace should be re-configured in favour of the bike

In many situations, right hand turn pockets are introduced simply because the space exists. Right hand turn pockets should only be included on roads where traffic delay is a real concern (i.e. on higher order collector, or distributor roads).

Careful attention is required to the provision for cycling in the vicinity of right hand pockets, where there may be local traffic weaving and turbulence.

It may not be feasible to re-engineer much of the existing urban space to provide for segregated facilities.

Integrated cycling solutions, based on the hierarchy of provision, are likely to be more effective in terms of cost and delivery. However, integrated facilities are likely to require significant changes to the traffic regime.

The transport implications of significant reductions in speed and volume of traffic on key arteries to and through cities and towns needs to fully understood and planned for, within the sustainable urban traffic plan, before embarking on such changes.