Archived decisions

Contact: Adrian Gray, ext 6892

1. Summary

1.1 Over recent years congestion has increased along the A32 due to greater traffic volumes. A number of traffic signal junctions have been installed to manage traffic joining from the side roads. Concern has been expressed over the level of congestion and questions asked as to what extent the Hampshire SCOOT (Split Cycle Offset Optimisation Technique) Urban Traffic Control System (UTC) is being or could be utilised to obtain the maximum efficiency from this section of road. This report sets out the current position in relation to UTC on the A32, what is currently proposed and the scope for future developments.

2. Background

2.1 On the A32 between Quay Street and Rowner Road/Elson Road there is a total of eight traffic signal junctions and five Pelican/Toucan crossings, as illustrated on the attached plan.

These are located as follows:

(i) Traffic Signals:

(a) Quay Street Roundabout;

(b) Salterns Lane;

(c) Fareham Reach;

(d) Wych Lane;

(e) Lederle Lane;

(f) Cunningham Drive;

(g) Fraters Gate/Tichborne Way; and

(h) Forest Way (Priddy's Hard); and

(ii) Pelican/Toucan Crossings:

(a) Earls Road;

(b) Lederle Lane;

(c) Fleetlands;

(d) North of Forest Way (Toucan); and

(e) South of Forest Way (Toucan).

2.2 UTC can be applied to closely-spaced junctions and Pelican crossings to coordinate traffic between junctions, and to ensure that the random effect of isolated junctions can be eliminated. Where junctions are more than 250 metres apart the benefits that can be obtained are reduced, and generally linking through UTC is not utilised.

2.3 The Hampshire UTC System comprises a central computer located in Winchester, and outstation equipment located at individual junctions and pedestrian crossings linked by British Telecom telephone circuits. SCOOT is the software developed by the Transport Research Laboratory (TRL) to optimise adjacent traffic signals in urban areas, and operates through the UTC system.

2.4 SCOOT uses traffic sensors at each junction to monitor traffic volumes and congestion, adjusting the length of time individual approaches receive the green light, the progression along the principal route and the overall recurrence at which all junctions operate, to minimise delay for the majority of traffic. In practice this means increasing the green period for the main road and ensuring the main road stages are coordinated at each junction. The overall time is usually constrained to limit delay for pedestrians.

2.5 In general SCOOT UTC provides the most efficient strategy for the control of traffic. However, in extremely congested conditions SCOOT cannot optimise the signal timings because of competing demands. In the case of these extremely congested conditions it is more effective to introduce a fixed time plan through UTC to manage the traffic. This technique of SCOOT operation, for the majority of traffic conditions throughout the day with fixed time plans, controlled by UTC in heavily congested conditions, is used both nationally and locally in Hampshire to good effect.

3. Current Operation

3.1 SCOOT UTC currently operates during the off-peak period (0930 to 1530 hours), Monday to Friday at the Cunningham Drive, Lederle Lane, Wych Lane and Fareham Reach junctions with the A32. During the morning and evening peak periods fixed time UTC plans are being developed and during the rest of the day the signals operate in isolated mode. However, the time of operation, methods, etc are reviewed regularly.

3.2 The current green time given to the side roads joining the A32 has been monitored, following concerns expressed that the timings are encouraging traffic to divert from the A32 to the side roads. The relatively small queues on the side roads, in comparison with those on the A32, is one factor giving rise to these concerns. During both the morning and evening peak periods the duration of the green time for Cunningham Drive, Lederle Lane, and Fareham Reach does not exceed 11 seconds. At Wych Lane the duration was up to 20 seconds, but Wych Lane runs concurrently with the A32 southbound. The A32 northbound is stopped for longer than the A32 southbound, due to the operation of right turn facilities at Cunningham Drive and Wych Lane, which operate more frequently than the equivalent right turn stages provided at Lederle Lane and Fareham Reach.

4. Future Proposals

4.1 Work is in hand to introduce SCOOT UTC at the Forest Way junction, recently constructed to service the Priddy's Hard development, together with the adjacent Fraters Gate junction, and these two junctions will be coordinated to optimise their operation. There is a planning application currently being considered in respect of the Fraters Gate area that would modify this junction, and the operation of SCOOT could be adjusted to reflect these changes and provide priority for traffic on the A32. The degree of priority at this junction, and the Forest Way junction, would need to balance the needs of pedestrians.

4.2 The traffic control strategy and design of junctions associated with South Hampshire Rapid Transit Phase 1 is currently being developed, and it is envisaged that a UTC strategy will be employed at junctions used by both the trams and other traffic once the Light Rapid Transit (LRT) is operational. The street-running section of the LRT scheme joins the A32 at Albert Street and its operation is not expected to significantly affect the operation of the A32 junctions north of Rowner Road. However, the construction of the LRT route, and particularly the alterations to the Newgate Lane flyover, will cause delay during the construction period.

4.3 In addition to the above, a study is currently investigating the scope for providing improved bus priority along the A32 and, whilst the result of this study is not known, it seems likely that operation of the traffic signals would be affected by any recommendations. Within the SCOOT UTC system there is also the opportunity to introduce bus priority whilst retaining the coordination benefits of UTC.

5. Scope for Improvement

5.1 The operation of UTC on the A32 is regularly reviewed, particularly when new junctions, etc are introduced, and a number of opportunities have been identified. The operation of the SCOOT system could be extended to operate on Saturday and Sunday. There is also scope to consider operating SCOOT during peak periods from Monday to Friday, but the present level of congestion suggests that any improvements would be marginal. As an alternative, fixed time UTC plans are being introduced and developed that will coordinate operation of the traffic signals during peak periods. Any such plans would effectively be a congestion management tool, as the volume of traffic on the A32 is such that the capacity of the road itself has been reached, and the opportunity for gaining maximum efficiency is limited. There is also a balance to be achieved between reducing car journey times and providing safe crossing points for pedestrians. The recommendations of the current study into bus services may also limit the scope for increasing the duration of green time on the A32. Notwithstanding the above, there are other factors affecting the operation of the A32, including the Old Gosport Road and Quay Street roundabouts.

6. Conclusion

6.1 Some coordination for traffic on the A32 is already being obtained through the SCOOT UTC system and work is underway to incorporate new traffic signal junctions within the UTC system, as appropriate. Work is also in hand to review the UTC Control Strategy, using both SCOOT and fixed time UTC plans, and to introduce new facilities and timings where appropriate.

6.2 The levels of traffic on the A32, particularly during peak periods, result in high levels of congestion because the capacity for this road is exceeded by the demand placed on it. SCOOT and UTC can ensure that the maximum capacity is achieved, but in situations of severe congestion there is little that can be introduced to significantly improve the situation. However, through the techniques and opportunities identified within this report, every effort is being made to ensure that the appropriate UTC strategy is applied on the A32 to maximise the available capacity.

Recommendation

That the report be noted.

7484/ARG