Traffic Data Surveys_Guidance and Request Form
Argyll and Bute Council · 20 March 2025
Back to Environment, Development and Infrastructure Committee — 20 March 2025 and its agenda
Text extracted from the council's PDF. Layout and reading order may differ from the original.
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APPENDIX 1 ROADS AND INFRASTRUCTURE SERVICES Traffic Data Surveys Guidance and Request Form Author Stuart Watson Owner Head of Roads & Infrastructure Services Date October 2021 Version 1.0
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1.0 Introduction The Service undertakes traffic surveys using traffic data units (radar traffic classifiers). The Units are located on street furniture (street lighting columns, sign poles etc.) and the data is collected for 24 hours per day over a set period (usually 5 or 7-days) as considered appropriate. The data collected includes vehicle speed, traffic volume and vehicle length. The Service receives a large number of requests for surveys each year and these will generally be prioritised based on road hierarchy. The Service will not, in normal circumstances, accept a request from an individual member of the public; requests for traffic surveys should normally be made through Local Members (Councillors) or via the local Community Council. Where there is significant representation from a local group, consideration may be given to a traffic survey. Where the requester believes the traffic is dangerous (e.g. high speeds in a housing scheme) then the initial report should be made to Police Scotland for action before requesting a traffic survey. Any changes to a speed limit will be made in reference to the Road Speed Limit Policy Framework but, for clarity, the setting of speed limits should be evidence led and reinforce peoples assessment of what is a safe speed to travel. This document takes into account the approaches set out in national technical and guidance documents; including CA185 Vehicle Speed Measurement (replacing TA 22/81 Vehicle Speed Measurement On All Purpose Roads) and the ETLLD Circular No. 1/2006: Setting Local Speed Limits. In-line with the guidance set out in the Policy and for the avoidance of doubt, the Roads Authority uses the mean speed of vehicles as the assessment criteria when considering a charge of speed limit. 2.0 Site Selection The selection of a suitable site is important, using a wrong location for a survey can distort results rendering the data effectively useless (for example, collecting data at the approach to a corner or give way markings where traffic naturally slows down). The following criteria must be considered when requesting a survey and will be used by Officers when assessing the survey location: • Traffic surveys will only normally be carried out within 20 mph, 30 mph and 40 mph speed limits. A lack of street furniture (e.g. sign poles) may impact the location of traffic surveys (i.e. the Service will not, generally, incur additional costs of installing poles to allow survey equipment to be sited at a particular location) o Where there is a need to carry out a survey within higher speed restrictions a risk assessment may be carried out prior to agreeing to the survey. o If a site is considered too high risk, in regards to staff safety, the survey will not be carried out. o If there is an identified need for additional traffic management to allow access for staff, the cost of this may be recharged to the requester. o If the proposed site is not suitable, Officers may opt to select the nearest appropriate location to the requesters proposed site. • Sites must be at least 100 metres from a change of speed limit.
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• Site location must offer an unobscured view of the running lane or lanes. • A minimum clear distance of 1 metre between the survey equipment and the edge of carriageway must be available. Any reduction of this distance can have an impact on the accuracy of data. • Subject to Table 1 below, traffic surveys will only normally be carried out during Neutral Months and will seek to avoid school holidays and large events to avoid a distortion of the data. The impact on data arising from surveys carried out outside neutral days or months will a key consideration during the assessment of survey results o A “neutral day” is a weekday between March and October excluding public holidays and school holidays. These are the days where traffic is expected to behave in a similar way. Normally, the traffic surveys will seek to capture a mix of both weekend and weekday traffic data. o A “neutral month” is defined as being one of: April, May, June, September or October. o In all cases, surveys will not be carried out over the Christmas period. o In addition to events (markets, races, charity days etc.) surveys will also not be carried out during periods where roadworks have commenced or where the road is being used as a diversion route for works on other parts of the network. Table 1 Route Description Restrictions Strategic routes Neutral months only Main Distributor Neutral months only Local Distributor Neutral months only where highly trafficked, all year where traffic volumes are considered to be low. Main Residential Street All year – depending on use/function, e.g. where it is only local access and flow etc. does not vary significantly from month to month. Minor Residential Street, Home Zone and Cul-de-sac All year – e.g. housing/residential area where daily traffic flows are generally the same. • Risk assessment / Safe Working Method o The generic risk assessment and safe working method provides the general known risk and mitigation methods. o Each site must be assessed prior to setting up a survey using the site specific assessment sheet. o High speed (>41mph) routes will generally require additional safety mitigation measures, e.g. traffic management, to ensure staff safety. • The following locations should be avoided, generally: o Sharp bends and steep gradients where vehicles may be accelerating or decelerating sharply.
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o Near traffic signals, junctions, pedestrian crossings and other similar features. o Near bus stops or similar where a stopped vehicle would obscure the radar function of the data units. • Requesters must be specific in regards to the location of a traffic survey as a repeat survey will not be carried out within 5 years unless there is a material change in circumstance (examples below): o A crash picture has emerged (cluster sites). o A new development has been completed (e.g. a new housing scheme or industrial/commercial operation). o Traffic behaviour has changed due, for example, to long term road closures, diversion routes and so on and are likely to continue into the future for a significant time period. o The road geometry/engineering has changed, for example, due to changing to a one way street, realignment, redetermination and so on. o A new speed limit has been introduced. 3.0 Survey Results The traffic surveys will normally collect mean speeds, 85th%ile speeds, traffic volumes and vehicle classification data. The data provided to the requester will be limited to mean speed and traffic volume only in most circumstances. Mean speeds, in accordance with the Policy and national guidance, is the principle speed data used when considering the setting of a speed limit. Speed Data Table 2, below, provides indicative thresholds for no action or intervention but must be considered alongside other factors. As noted above, mean speeds are used to determine the suitability of an existing speed limit, however, mean speeds should not necessarily be used in isolation when considering the setting of an appropriate speed limit. Each site should be assessed on its own merits. The following factors have varying degrees of importance (not exhaustive): • Road function (e.g. distributor road, local access road) • Road geometry (width, sightlines, bends, junction, accesses, footway provision etc.) • Road environment (rural, urban, residential, shop frontages, schools, public buildings) • Level of frontage access development (i.e. direct access from the property to the public road). Distance from the carriageway edge to the dwelling will be included in the assessment (e.g. properties set back more than, say, 20m will not normally be considered as frontage properties) • Traffic composition (cycles, pedestrians, light vehicles, HGVs etc.). Use as a public transport or emergency service route is also an important factor. • Accident history (3 & 5 years normally) including severity of injuries and any cluster sites • Public perception • Feasibility of providing physical traffic management measures • Impact arising from any proposed traffic management on public transport passenger comfort and emergency service response times
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• Visual impact of sign clutter and other physical measures on the local environment • Police Scotland’s ability to support enforcement Table 2 Existing Speed Limit (mph) No further action if mean speed is within range Consideration for intervention above* 20mph 20-24mph 25mph+ 30mph 30-35mph 36mph+ 40mph 40-46mph 47mph+ *subject to other factors as noted above A new 20mph speed limit will only be considered when current mean speeds are already 24mph or below; except for new housing developments where the developer is introducing appropriate traffic calming measures as part of the RCC or Planning requirements, i.e. traffic management measures that will encourage lower speeds to be realised. Speed limits should not be used to attempt to solve the problem of isolated hazards, for example, a single road junction or reduced forward visibility at a bend. Speed limits will not necessarily be reduced where mean speeds are lower than the posted limit; for example, if speed survey returned a mean speed of 28mph in a 40mph limit, it would not always automatically follow that the speed limit should be amended to a 30mph speed restriction. Note, where speeds exceed the current limit, it may be a legitimate solution to increase the speed limit rather that introduce traffic management measures (i.e. acknowledge the existing speed has been initially set incorrectly). Detailed speed survey data will be shared with Police Scotland for action as they consider appropriate. This will include bracketed recorded speeds which will allow Police Scotland to focus enforcement activity as they consider appropriate. Traffic Volume Generally, traffic volumes within Argyll and Bute, even on A-Class routes (local and trunk roads) are low compared within national figures, however; where there is a case supported by data that volume is having a detrimental impact consideration will be giving to mitigation. This will normally be assessed against other data including available alternative routes, accident data, mean speeds, vehicle types and public perception.
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4.0 Appendix 1 – Traffic Survey Request Form Note: Where the requester believes the traffic speed or behaviour is dangerous then the initial report should be made to Police Scotland for action before requesting a traffic survey. Request Details (note, please provide an individual request per site) Date of Request: Name of Requester: Community Council or Member request Telephone no.: Email address: Traffic Issue (tick all that are relevant) Speeding Traffic Volume Vehicle Type Please provide further detail of the issue(s) and the desired outcome: e.g. cars racing at along Fast Street between no. 41 and no. 75. Usually occurs between 14.00 to 22.00. Young children playing in the street and crossing from school bus drop off. We have received 10 complaints from the 13 houses fronting the road at this location. The road needs a speed bump and better signs.
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Survey Location: Road Class and Number and Street Name: e.g. C67 Lorne Street Town / Village / Settlement (or if rural, then nearest) e.g. Lochgilphead Current Speed Limit: e.g. 30mph Provide description of preferred survey location: e.g. Between no. 1 and no 7 Lorne Street Please provide a plan, photos or any other information which would help locate the survey: Other info: Plan: I confirm that I have read and understood the information provided in the guidance document (please tick) Signed: Print Name: Role: e.g. Secretary of Community Council or Ward 1 Member This form should be completed and submitted by email to Traffichq@argyll-bute.gov.uk. Failure to provide sufficient detail will result in the survey request being declined.