TRANSPORT AND TECHNICAL SERVICES
Traffic Signal Replacement Programme
Progress Report
Purpose of the Report
To note the current position with regard to the programme to replace and upgrade four traffic signal controlled junctions, and to formally gain the Ministers approval for the improvements, as agreed, at the following road junctions.
The progress to date is as follows: -
Plat Douet Road / Green Road – site work in progress
Route du Fort / St Clement’s Road – site work expected to begin in July
St Saviour’s Road / Simon Place – complete and performing well
Hill Street / Halkett Place. – site work in progress
Background
The Minister has previously agreed to upgrade the above listed traffic signal junctions as part of the 2006 road improvement scheme programme (see MD-T-2006-0016.) The Minister requested further information on the recommendations made at the signal junctions at St Saviour’s Road / Simon Place, and Hill Street / Halkett Place. Following discussions with the Officers involved, the recommendations have been implemented. Since that discussion, further detailed design and option evaluation has taken place with regard to the signal junction Route du Fort / St Clement’s Road. This paper sets out these pros and cons and the reasons for the decisions made for each of the junctions.
Traffic signal equipment at these junctions is due for replacement. The equipment age varies between 15 to 25 years old and has past its design life. Maintaining the equipment is becoming increasingly difficult due to a lack of spare parts.
It would be possible to just replace the signals at these junctions without changing the way in which they operate, or providing additional facilities for pedestrians. The following discussion outlines the different options (following detailed analysis of traffic flows and delays based on the LINSIG computer design software) available for each junction as well as a recommendation.
Discussion
Plat Douet / Green Road Junction, St Clement
TTS requested a road widening scheme be undertook as part of planning permission granted to the Jersey Recreation Ground Company Ltd in respect to St Clement’s Golf and Sport Centre. The road widening scheme would have added an extra left turn filter lane to Plat Douet Road southbound.
Planning and Building Services did not consider the request appropriate to apply a condition requiring that the road widening be implemented
The junction accident record shows 3 slight accidents involving injury to vehicular occupants occurring between 2000 and 2005. It has no history of pedestrian accidents, and currently has no signalised pedestrian crossings. There have been requests from members of the public and parish officials for controlled pedestrian crossings. A survey of pedestrian movements has highlighted a demand, particularly across La Grande Route de St Clement.
The LINSIG traffic model shows that the junction currently has adequate practical reserve capacity (PRC) during the morning rush hour (23%) but has no spare capacity during the evening rush hour (-13.5%.)
In order to provide a controlled pedestrian crossing it is necessary to include an “all red to traffic” stage, as it is not possible to incorporate pedestrian phases which would run parallel to traffic phases. The traffic model shows that this would reduce the junction’s capacity on average by 13% and increase the total delay by 4.5 passenger car unit hours. Due to the long cycle time it would be preferable to include the pedestrian stage twice a cycle, however the added delay to motorists would become unacceptable and as such it is not recommended.
Options
1. Replace signal equipment with like for like.
2. Replace the signal equipment and add an all red pedestrian stage once per cycle.
Recommendations
It is recommended to follow option 2. Construction work has now commenced to implement this proposal.
Route du Fort / St Clement’s Road Junction, St Helier
The junction accident record shows 4 slight accidents involving injury to vehicular occupants occurring between 2000 and 2005. It has no history of pedestrian accidents, and currently has no signalised pedestrian crossings. The junction does have pedestrian refuges to assist in crossing La Route du Fort. A survey of pedestrian movements is attached to this report.
The right turn movement from Route du Fort Eastbound to St Clement’s Road does not have its own traffic phase. The predominant right turn from La Route du Fort westbound to St Clement’s Road (northbound) does have a green filter arrow. Vehicles wishing to make this movement are opposed by traffic along La Route du Fort westbound. Several motorists have expressed concern to the Department as to the safety of this manoeuvre.
The LINSIG traffic model shows that the junction currently has a PRC during the morning rush hour of 5% and has less capacity during the evening rush hour -6.8%. The minimum desirable PRC is 20%, anything less will result in a degree of queuing.
It would be possible to improve the uncontrolled crossing facilities at the junction by reducing the carriageway width at the northern arm of St Clement’s Road and the western arm of Route du Fort. In order to provide a controlled pedestrian crossing across either arm of St Clements Rd it is necessary to include an “all red to traffic” stage. Staged controlled crossings could be used to allow pedestrians to cross Route du Fort but are not recommended.
Options
1. Replace the signal equipment with like for like. Uncontrolled pedestrian facilities would be improved as part of the works.
2. Replace the signal equipment and include an “all red to traffic” stage. In addition a traffic phase would be added for the right turn movement from Route du Fort eastbound to St Clement’s Road. This additional phase would require the straight through traffic movements on La Route du Fort to be stopped while the right turn phases are green. This will remove the option for motorists to turn right in gaps between the oncoming traffic. The model shows that this would reduce the junctions PRC by around 45%, and increase the total delay by approximately 32 passenger car unit hours.
3. Replace the signal equipment and add a traffic phase for the right turn movement from Route du Fort eastbound to St Clement’s Road, but to omit the addition of pedestrian phases. The model shows that this would reduce the junctions capacity by around 20% and increase the total delay by approximately 8 passenger car unit hours. Uncontrolled pedestrian facilities would be improved as part of the works.
A survey was undertaken into the right turn movements across the junction. It showed that a large proportion (up to 40%) of eastbound vehicles turned right during gaps in the opposing traffic flow, instead of waiting for the green filter arrow. Options 2 and 3 would restrict the amount of time vehicles would be allowed to make this movement by only allowing right turn movements when the green arrow appears.
Using data from the survey, predictions of the queue lengths in the right turn lanes of Route du Fort were made. The maximum predicted average queue lengths in an hour were 4.5 vehicles eastbound, and 8.6 vehicles westbound. These figures are for an average queue length, at times the queue would be larger or smaller.
The geometry of the junction allows 7 cars to queue in the right turn eastbound lane of Route du Fort before other vehicles are blocked. 9 cars can queue in the westbound right turn lane before other vehicles are blocked. Commercial vehicles, busses etc would reduce the number of vehicles able to queue without causing an obstruction to through traffic.
The predicted average queue lengths (particularly the westbound figures) show at times the queue in the right turn lane will become large enough to restrict traffic flow through the junction. This would substantially affect the capacity of the junction and could potentially lead to large delays for motorists. It is not possible to accurately quantify the delays with the traffic modelling software.
The junction is situated on the ring road, as such the delays to traffic caused by the introduction of an “all red to traffic” stage (option 2) would be unacceptable. A signalised right turn stage at the junction may reduce the numbers of right turning vehicles at Roseville Street and Cleveland Road, with associated capacity and safety benefits. However the estimated queue lengths show that at peak times the delay to motorists would be unacceptable.
Recommendations
It is recommended to follow option 1. In order to minimise the possibility of motorists who turn right from La Route du Fort eastbound, to St Clement’s Road southbound misreading the significance of the signals, it is proposed to re-locate the secondary signal from the central refuge to the north side of the junction. (As shown on Fig. 1.) This will reduce the likelihood that these motorists may make the incorrect assumption that opposing traffic has been signalled to stop.
A right turn filter arrow would still be included for westbound traffic turning north into St Clement’s Road. Motorists using La Route du Fort would retain the option to turn right during gaps in the opposing traffic flow in both directions.
St Saviour’s Road / Simon Place Road Junction
The junction accident record shows 3 slight accidents involving injury to vehicular occupants, and one injury to a pedestrian occurring between 2000 and 2005. It currently has no signalised pedestrian crossings.
The junction is slightly staggered, the Simon Place and Woodville Avenue traffic phases currently occur in the same traffic stage. This causes a conflict between motorists turning right from Woodville Avenue, and right from Simon Place. There are no records of injury accidents caused by this, but it is of concern to the Department as several complaints about “near misses” attributed to this movement have been received from motorists.
The pedestrian crossing survey shows a particular demand across the northern arm of St Saviour’s Road and across Simon Place.
The LINSIG traffic model shows that the junction currently has adequate PRC during both the morning rush hour and the evening rush hour (approximately 70%.)
In order to provide a controlled pedestrian crossing it is necessary to include an “all red to traffic” stage. The traffic model shows that this would reduce the junctions capacity on average by 38% and increase the total delay by 2 passenger car unit hours. This would allow controlled pedestrian crossings to be installed across all arms of the junction. However due to very light vehicular use a crossing is not recommended to be installed across Woodville Avenue. Due to a lack of pedestrian demand a crossing is not recommended to be installed across the southern arm of St Saviour’s Road. This would reduce the number of poles, detectors and pedestrian heads needed to be installed at the junction. This would also reduce the maintenance cost, and visual impact of the junction.
Options
1. Replace the signal equipment with like for like.
2. Replace the signal equipment and include an “all red to traffic” stage. (Reducing the junctions capacity on average by 38% and increasing the total delay by 2 passenger car unit hours.)
3. Replace the signal equipment, include an “all red to traffic” stage, and to separate the Simon Place and Woodville Avenue traffic phases. This would reduce the junctions capacity on average by 45% (the model shows a current average PRC of 75%) and increase the total delay by 4 passenger car unit hours.
Recommendations
The LINSIG model shows that option 3 has sufficient reserve capacity to separate the traffic phases and to include an “all red to traffic” stage without causing significant delays to motorists. This proposal has been implemented on site and is working successfully.
Hill St / Halkett Place
The junction accident record shows no accidents involving injury to vehicular occupants or pedestrians occurring between 2000 and 2005. It currently has no signalised pedestrian crossings.
A pedestrian survey has shown a particular demand to cross Halkett Place from the road junction with Hill St to the entrance to the Royal Square.
Due to there being only one conflicting traffic movement (vehicles approaching from Snow Hill or Halkett Place, must continue along Hill Street) the option of removing the traffic signals and replacing them with a filter in turn arrangement with zebra crossings has been explored. Although this arrangement may cause less delay to motorists at quiet times, the uphill gradient of Halkett Place approaching the road junction would force motorists to “stop and hill start” frequently due to pedestrians crossing the road, and whilst filtering with traffic approaching from Hill Street. This operation is therefore not recommended.
Options
1. Replace the signal equipment with like for like.
2. Replace the signal equipment, and install controlled pedestrian crossings across the eastern arm of Hill Street, and across Halkett Place. The addition of the crossings can be achieved without any additional delay to motorists as they would operate concurrently with the vehicle stages.
Recommendations
It is recommended to follow option 2. Construction work has now commenced to implement this proposal.
Costs
90% of the signal control equipment was purchased late in 2005. The cost of the associated civils work, and the purchase of the remaining equipment and services required is estimated to be £113,000.
Funds are available from capital votes CO303 – Road Improvement Schemes and C2680 – Traffic Signal Replacement.
The following are the estimated costs :
Plat Douet / Green Road £15,000 civils work £10,000 Signal equip.
Route du Fort / St.Clement's road £22,000 civils work £8,000 Signal equip.
St.Saviour's Road / Simon Place £20,000 civils work £7,000 Signal equip.
Hill Street / Halkett Place £18,000 civils work £13,000 Signal equip.
Approximately £3,000 in miscellaneous goods / service for the above works
Capital vote CO303 – Road Improvement Schemes Total £75,000
Capital vote C2680 – Traffic Signal Replacement Total £41,000
Total expected spend approx. £113,000
Recommendation
The Minister is recommended to endorse his officers’ proposals to improve these junctions: -
Plat Douet Road / Green Road, Option 2
Route du Fort / St Clement’s Road, Option 1
St Saviour’s Road / Simon Place, Option 3
Hill Street / Halkett Place, Option 2
Reason(s) for Decision
To replace and improve deteriorating traffic signal equipment at 4 junctions, on roads administered by the Department
Action Required
Officers to make arrangements to carry out the work required to complete the proposed improvements.
Written by: | Ross Fearnley |
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Approved by: | Chris Sampson, Director - Municipal Services |
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Endorsed by: | Dave St George, Transport Policy Manager - Transport |
Attachments: Pedestrian movement survey and traffic signal stage sequence for each signal controlled junction.
Traffic Signal Replacement Program LINSIG Results
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[30th May 2007]
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