The UK standard for assessing cycling infrastructure quality using 25 scored indicators across five design principles.

The Cycling Level of Service tool assigns every indicator one of three scores: 2 (Green) for high quality or best practice, 1 (Amber) for minimum acceptable standard, and 0 (Red) for critical or unacceptable conditions. This traffic light approach was deliberately chosen to make assessments immediately legible to non-specialist audiences, including councillors, planning officers, and community stakeholders. A Green score of 2 represents infrastructure that meets the full recommended standards found in LTN 1/20 and is safe for all abilities, including children aged 8 and adults aged 80. Examples include fully separated cycle tracks, traffic speeds below 20 mph, smooth machine-laid asphalt surfaces, and well-lit routes throughout. The design philosophy behind the Green threshold is that cycling should require no more skill or courage than walking.

An Amber score of 1 indicates the minimum acceptable standard. The infrastructure meets basic requirements but may have minor issues or require higher cyclist skill and confidence. Examples include light segregation with wands or planters, some delay at signalised junctions, hand-laid surfaces with minor joints, and routes with infrequent unlit sections. Amber scores are tolerable in small numbers but an accumulation of Amber ratings across multiple indicators signals that the route, while not critically dangerous, falls short of inclusive design and may deter less confident riders. A Red score of 0 represents conditions that are critical or unacceptable and do not meet basic safety or quality requirements. Examples include sharing traffic lanes with vehicles travelling above 37 mph, cycle lanes in the dangerous 3.2-to-3.9-metre "murder strip" range, routes with disconnected sections requiring dismounting, and significant kerbside conflict zones adjacent to parking. Several Red scores carry the additional penalty of being designated Critical Fail conditions, which override the total percentage score entirely.

The total assessment score is calculated by summing all 25 indicator scores, producing a result between 0 and 50 points. The percentage is derived by dividing the total by 50 and multiplying by 100. To pass the CLoS assessment, a scheme must achieve at least 70% (35 out of 50 points) and must not trigger any Critical Fail condition. A route scoring 45 out of 50 (90%) still fails if it scores Red on Junction Speed (Criterion 9) because that specific indicator carries a Critical Fail designation. This dual-gate mechanism ensures that schemes cannot compensate for genuinely dangerous conditions by accumulating high scores on less safety-critical indicators like signing or street clutter.

The official LTN 1/20 documentation is published by the Department for Transport (DfT) and defines the national design standards for all cycling infrastructure in England.

The surface quality indicators (Criteria 17-18) closely relate to methodologies in the UKPMS CVI road condition survey, which can provide more detailed pavement condition data for cycling routes.

Under LTN 1/20, certain indicators are designated as Critical Fail conditions. When any of these indicators receives a Red score (0 points), the entire scheme is classified as "FAIL (Critical)" regardless of the overall percentage score. A route could achieve 45 out of 50 points — a 90% score that would comfortably exceed the 70% threshold — but if it scores Red on a single Critical Fail indicator, the scheme is ineligible for Active Travel Fund or similar government funding. This mechanism exists because the consequences of certain design failures are so severe that no amount of good design elsewhere can compensate for them. Forcing cyclists to share traffic lanes at speeds exceeding 37 mph, for example, creates a lethal collision risk that cannot be offset by excellent signing, smooth surfaces, or abundant cycle parking.

The Critical Fail indicators include: Criterion 4 (Deviation) where the cycle route is more than 1.4 times longer than the direct motor traffic alternative, making cycling uncompetitive; Criteria 9 and 10 (Junction Speed and Link Speed) where 85th percentile motor traffic speeds exceed 37 mph (60 km/h) in shared or adjacent conditions; Criterion 11 (Traffic Volume) where AADT exceeds 10,000 vehicles or HGV composition exceeds 5% without adequate segregation; Criterion 12 (Segregation) where the nearside lane falls within the 3.2-to-3.9-metre "murder strip" range that prevents safe overtaking; Criterion 13 (Junction Conflict) where frequent side roads or major junction movements are untreated; Criterion 15 (Kerbside Activity) where the cycle lane is under 2 metres wide adjacent to parking, creating a dooring zone; and Criterion 19 (Effective Width) where more than 25% of the route is significantly below the minimum desirable width. In the digital form, selecting a Red score on any Critical Fail indicator triggers an immediate warning: "CRITICAL FAIL DETECTED: Scheme is ineligible for funding." The inspector cannot override this warning — it is a hard-coded validation rule.

Many local authorities publish guidance on applying LTN 1/20. For Essex-specific guidance, see the Essex Active Travel Design Portal. For a broader overview of how local authorities apply the CLoS tool, see standards directory.

An LTN 1/20 CLoS assessment begins by dividing the route into homogeneous links — sections where the road characteristics remain broadly consistent. A link might be a 300-metre stretch of off-carriageway cycle track between two junctions, or a 500-metre segment of mixed traffic on a residential street. When the infrastructure type changes (for example, from a stepped cycle track to an advisory cycle lane), a new link begins. Each link is scored independently against all 25 indicators. The inspector first records the Route Context for each link: the infrastructure type (from eight options ranging from off-carriageway track to mixed traffic on a busy road), the posted speed limit, the 85th percentile measured or estimated speed, and the AADT motor traffic volume. These contextual fields drive several indicator scores — for example, the speed limit and AADT directly inform Criteria 9, 10, and 11.

The inspector then works through the 25 indicators in order, assigning Red, Amber, or Green to each based on the field conditions observed and any measurements taken. For width-related indicators (Criteria 12 and 19), multiple spot measurements may be needed along the link to determine compliance. For speed indicators (Criteria 9 and 10), the 85th percentile speed may be measured with a radar gun or estimated from traffic count data. Defects observed during the assessment — potholes, width pinch points, signing gaps, safety hazards — are logged in the repeatable Defects & Photos section with evidence photographs. Each defect is classified by type (Surface Defect, Width/Pinch Point, Signing/Lighting Issue, or Safety Hazard/Critical Fail) and documented with mandatory photo evidence and optional notes. The system then automatically calculates the Total Score (sum of all 25 indicators, maximum 50), the Percentage ((Total/50) x 100), the Critical Fail Count (number of Critical Fail indicators scored Red), and the Overall Result: "PASS" if the percentage is 70% or higher and the Critical Fail count is zero, "FAIL (Score)" if below 70% with no critical fails, or "FAIL (Critical)" if any Critical Fail indicator is Red.

For design verification of proposed schemes, the assessment can be conducted on paper using design drawings and traffic modelling data rather than field observation. The same 25 indicators apply, but the evidence comes from design specifications rather than site measurements. This dual-use capability — field audit and design verification — makes the CLoS tool both a retrospective quality audit and a prospective design gate. Local authorities across England use CLoS scores as a binding requirement for Active Travel Fund applications, and many authorities have adopted the tool for all cycling infrastructure regardless of funding source. The assessment is typically performed by transport planners, highway engineers, or cycling officers with training in LTN 1/20 methodology.