40 mph buffer zone - Poortown Road

Summary

The requester asked for justification regarding the use of 2011 traffic data and evidence of officer experience and police support for a 40mph buffer zone on Poortown Road. The Department of Infrastructure responded by providing all requested information, including a 36-page guidance document on speed limits and traffic calming thresholds.

Key Facts

• The Department of Infrastructure confirmed that all information regarding the Poortown Road buffer zone was sent.
• The decision to introduce the buffer zone was based on traffic speed data, officer experience, and police consultation.
• The response included a guidance document (GN-06-026) detailing criteria for implementing speed limits and traffic calming measures.
• Traffic calming measures are required for a 40mph limit if the 85th percentile speed surveyed is 46mph or higher.
• The guidance document was signed off by the Director on 17 May 2018.

Data Disclosed

• 40 mph
• November 2011
• 22nd March 2021
• 1931989
• 1680990
• 2021-08-02
• 2021-08-20
• 36 pages
• 5 documents
• 85th percentile
• 23 mph
• 35 mph
• 46 mph
• 58 mph
• 69 mph
• 19/07/2017
• 12/09/2017
• 27/09/2017
• 17/05/2018
• GN-06-026

Original Request

1. Why did the Department base its decision to use traffic speed date from November 2011, which was nine and a quarter years prior to the Department's response to a Freedom of Information Request ref: 1680990 dated the 22nd March 2021, when it decided to introduce a 40mph buffer zone on Poortown Road ? 2 Which officer's experience in traffic management was the Department relying upon in your response here - "The decision was made as a result of traffic speed data, officer's experience in traffic management and support from police consultation" 3. Please provide written evidence describing such officer's experience in traffic management and written evidence of submissions made by such person to the Department when it was considering introducing the buffer zone referred to. 4. Please provide copies of the support (for the buffer zone) which the Department says it received from police consultation. 5. Please provide a copy of whatever road traffic order makes provision for the buffer zone.

Data Tables (11)

Full Response Text

Appendix 1

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Issue/Rev Nr Date Owner Description 1 19/07/2017

SYSTRA draft report for internal review 2 12/09/2017

SYSTRA revised draft report for internal review 3 27/09/2017 BW Doc controlled and references added 4 17/05/2018 JR Director signed off

Guidance GN-06-026 Speed Limits Uncontrolled if Printed MF-00-036-1.0 Page 2 of 13

Purpose 1. The purpose of this guidance document is to describe the issues to be considered when implementing a new or revised speed limit, or deciding if a speed limit is necessary.
Highway Services speed limit policy document should be referred to for details on why a speed limit is needed.

1. This guidance applies to all speed limits on the island’s adopted roads, and proposed roads that are to be built as part of new developments that may be subject to a speed limit.

2. This document is intended to provide clarity on Highway Services requirements for speed limits, and it sets out the protocol for achieving this. Introduction

3. Speed limits are mandatory and require a Traffic Regulation Order (TRO) to be implemented. TROs follow a statutory process so that they can be legally enforced by the Police to stop high or inappropriate speeds on the public highway.

4. The criteria for introducing traffic calming measures with a specific proposed speed limit is shown in Table 1 below. It is based on a comparison of the 85th percentile speed surveyed and the proposed speed limit to be introduced. The 85th percentile speed is the speed at or below which 85% of all vehicles are travelling. The thresholds shown identify the speed at or above which traffic calming measures need to be introduced with the proposed speed limit.

Table 1: Thresholds for Introducing Traffic Calming Measures with a Proposed Speed Limit Proposed Speed Limit (mph) 85th Percentile Speed Surveyed (mph) Is Traffic Calming Required? (Yes/No) 20 <23 No ≥23 Yes 30 <35 No ≥35 Yes 40 <46 No ≥46 Yes 50 <58 No ≥58 Yes 60 <69 No ≥69 Yes

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1. Highway Services reserves the right to deviate from the criteria in Table 1. This will be done where Highway Services considers that traffic calming measures are required in conjunction with the proposed speed limit, even if the 85th percentile speed surveyed is below the threshold identified. This is likely to occur where there is a high accident record, a highway safety problem or particular local circumstances that could benefit from the installation of traffic calming measures and the associated reduction in vehicle speeds.

2. In order to introduce a 20mph speed limit where 85th percentile speeds are up to 23mph, then traffic calming measures are not required as the proposed 20mph limit should already be self-enforcing. Traffic calming measures will be required where the 85th percentile speed is at or above 23mph to enable the proposed 20mph limit to be self- enforcing and to avoid it needing Police resources to enforce it. Highway Services will consider local conditions and the accident rate when proposing a 20mph limit to make a decision on whether traffic calming measures should be provided.

3. The type of traffic calming measures to be introduced is discussed in more detail in the Speed Management Measures section below and in the Highway Services traffic calming policy and guidance documents. It is likely to be influenced by the level of reduction in vehicle speeds required as some measures will be more effective than others at achieving this. However, the general rule of thumb is lower speed roads will require vertical traffic calming measures such as road humps to provide greater speed reduction, and higher speed roads will use road markings and signage which have a lesser effect on reducing speed. Speed limits in between will have more flexibility in the range of measures that can be adopted, but are more likely to include horizontal traffic calming measures, such as road narrowings or road markings, which achieve some speed reduction.

4. Road humps, road cushions, rumble devices, speed tables and raised junctions will not be used on primary, secondary, district and local routes as these types of measures are typically unsuitable for use on main routes carrying higher volumes of traffic. In addition, these measures can adversely impact upon the response times of emergency service vehicles which will use these routes on a regular basis.

5. Speed limits are most commonly implemented in the following locations:

 Residential areas;

 Locations with a high accident record where speed was a contributory factor for the majority of accidents; and

 Sections of roads where a significant proportion of vehicles are travelling too fast for the nature and layout of the road under typical conditions (ie. due to bends in the road, a high number of accesses, poor forward visibility, etc.).

1. Speed limits are usually only implemented as a revision to current arrangements, irrespective of whether there is already a speed limit in place, where the need to restrict (or further restrict) speed can be demonstrated. There is often little demand to introduce a new speed limit as part of a new road or proposed highway scheme.

2. Section 125 of the Manx Highway Code states that the speed limit is the absolute maximum and does not mean it is safe to drive at that speed irrespective of conditions.
   Speed limits are not a minimum and are not to be treated as a target that motorists are encouraged to reach. It is often inappropriate or unsafe to drive at the maximum speed Uncontrolled if Printed MF-00-036-1.0 Page 4 of 13

limit as it depends on local conditions and variable factors such as the weather. Drivers should reduce their speed in the following circumstances:

 At or near junctions;

 Where forward visibility is limited, ie. on the approach to a bend;

 On narrow roads where the ability for two-way traffic may be difficult or not possible in certain places;

 Where there are no footways and pedestrians walk in the road;

 Snow and icy weather;

 Fog;

 Wet weather where visibility is impaired and / or the road surface is wet;

 During the hours of darkness;

 Where traffic calming measures are in place;

 Outside schools; and

 Where there are vulnerable road users present, particularly in large numbers or on narrow footways.

1. It should be noted that the above list is not exhaustive and only reflects the most common reasons for reducing vehicle speeds. Speed Limit Criteria

2. Highway Services sets speed limits at or up to 15 per cent lower than the 85th percentile speed. The 85th percentile therefore excludes the top 15 per cent of vehicles that are travelling at the highest speeds. This is good practice and excludes any vehicles that have been recorded excessively speeding which should not be accounted for when establishing an appropriate speed limit. As an example, an 85th percentile speed of 35mph would warrant a 30mph speed limit (ie. 15 per cent of vehicles are travelling above 35mph).

3. The extents of a speed limit are to be defined based on where the entry and exit signage would be visible to traffic entering the speed limit, or leaving the speed limit to enter an unrestricted stretch of road or a road subject to a different speed limit.

4. For a 30mph area, the entry and exit signage should be placed at the location where housing is close to both sides of the road. This is to define the change in nature of the road and the corresponding need to amend the speed limit to reflect local conditions.

5. When entering an urban area with a speed limit of 40mph or less from a derestricted or unrestricted area, a buffer speed limit of more than 300 metres in length must be installed. Alternatively, count-down markers to the 40mph or lower speed limit must be implemented. This provides motorists with a sufficient distance and period of time to reduce their speed to the approaching speed limit, which may be significantly lower than the speed they have been travelling in the derestricted area. Uncontrolled if Printed MF-00-036-1.0 Page 5 of 13

6. When the 85th percentile speed is in excess of 15 per cent above the proposed speed limit, buffer zones on the approach must include traffic calming measures. These measures may be road markings, road narrowings, electronic signage, rumble devices or gateways. This is discussed in more detail in the Speed Management Measures section below.

7. The extent of a speed limit will be desirable minimum of 600 metres and an absolute minimum of 300 metres. This is to ensure that there is a sufficient distance for the speed limit to be enforceable.

8. An environmental or safety speed limit may be installed at more than 15 per cent below the 85th percentile speed subject to the installation of appropriate traffic calming measures. This should enable the traffic speeds to be reduced to reflect the proposed lower speed limit, so speeds will hopefully correspond more closely with the proposed 85th percentile speed that will be in place after the revised lower speed limit is introduced.
   Experience suggests that introducing speed limits that are substantially lower than the 85th percentile speed will not be complied with, particularly in the longer-term, unless associated traffic calming measures are provided. Environmental speed limits may be implemented to improve the amenity of residential areas and local communities, particularly where there are likely to be high concentrations of vulnerable road users and road safety benefits of reducing vehicle speeds.

9. In areas that are not subject to a 20mph speed limit, a part-time 20mph speed limit will usually be introduced outside schools to reduce vehicle speeds during school opening and closing times only. These lower speed limits are adopted to take account of the significant changes in local conditions that occur during these short-term periods which include large increases in traffic, pedestrian crossing movements and vulnerable road users. Temporary speed limits are not used on the island apart from during highway works, or potentially a special event. A Temporary Road Traffic Notice is required to facilitate temporary road closures, prohibitions and restrictions of traffic. A Statutory Notice is needed to hold special events such as carnivals, parades and markets where speed limits may be temporarily suspended.

10. A restricted road is a road on which a speed limit is imposed. A derestricted or unrestricted road is a road outside a town or village district that has no speed limit.

11. The introduction of higher speed limits is only likely to be required where vehicle speeds on a stretch of existing derestricted road are generally too high for the nature of the road under typical conditions. In such circumstances, specifying a speed limit to encourage motorists to reduce their speed should assist in reducing the accident rate and problems caused by vehicles driving at higher speeds.

12. In order to introduce a new speed limit, a risk assessment of the speed on a particular section or sections of the road should be undertaken. The sections should be defined according to similar local conditions and suitable minimum lengths over which a new speed limit could potentially be introduced. The risk assessment should include a review of the traffic accident data for the last three years and site observations from one of Highway Services highway officers.

13. Due to the island being a tourist attraction which accommodates a lot of visitors, the likelihood of accidents occurring can increase as a result of motorists being unfamiliar with the island’s highway network. This can become particularly prevalent during the summer Uncontrolled if Printed MF-00-036-1.0 Page 6 of 13

months and peak periods of the tourist season. The imposition of appropriate speed limits can greatly assist visitors by informing them what speed they should be travelling at, rather than leaving them to choose their vehicle speed which has the potential to be misjudged.

1. Speed limits do not apply during the TT and road races when roads are closed to all other traffic. Temporary road closures include legislation to suspend speed limits for the temporary period identified in the Temporary Road Traffic Notice. Speed Limits at Specific Locations and for Particular Vehicles or Users

2. Section 124 of the Manx Highway Code states that a speed limit of 30mph applies to all traffic on roads in town or village districts unless a lower speed limit, ie. 20mph, applies to certain residential roads or motor vehicles of a certain class. The speed at which all vehicles must travel, apart from those of a particular class as stated in paragraph 31 below, is sometimes referred to as a general speed limit.

3. Section 208 of the Manx Highway Code states that in some places there may be a school warning or variable speed limit sign to inform drivers that there may be children crossing the road ahead. Variable speed limits are only installed outside schools where a lower speed limit can apply on a part-time basis during school opening and closing times. The usual higher speed limit will be in force at all other times. There are no other scenarios on the island where the permanent speed limit varies. The usual and part-time speed limits are stated in the TRO and are both enforceable at the times prescribed.

4. Permanent speed limits are often suspended during highway works, or for special events.
   Sometimes lower temporary speed limits need to be introduced at road works to protect the safety of the workers on the highway, or where newly resurfaced roads can only carry traffic at low speeds for a limited period to avoid potential damage. A Temporary Road Traffic Notice can be introduced to temporarily suspend or change a speed limit.

5. Annex 8 (page 150) of the Manx Highway Code states that on many greenlanes, a white speed limit notice advises motorcyclists not to exceed 20 mph. The speed limit is advisory and often introduced on greenlanes but not always. It is implemented principally for environmental

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