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PD CEN TS 15901 — Road and Airfield Surface Characteristics Skid Resistance Determination (Part 14 ViaFriction; Part 15 IMAG Longitudinal Controlled Slip Devices)
Road and Airfield Surface Characteristics — Skid Resistance Determination using Devices with Longitudinal Controlled Slip
🛣️ PD CEN/TS 15901 is a series of Published Documents issued by the British Standards Institution (BSI) based on the European Technical Specification CEN/TS 15901 for road and airfield surface characteristics, whose core content is the determination of skid resistance (anti-skid performance). The two parts covered in this batch, PD CEN/TS 15901-14:2016 and PD CEN/TS 15901-15:2014, specify test procedures for determining skid resistance using two measurement devices based on the “longitudinal controlled slip” principle — ViaFriction and IMAG. Such devices can measure pavement friction performance continuously and at high speed, providing important technical support for road and airfield safety management and pavement maintenance decisions.
💡 Skid resistance is the ability of a pavement surface to resist tyre sliding when wet, and directly affects braking distance and cornering safety. The CEN/TS 15901 series makes anti-skid indices comparable across different devices and sites by unifying the operating procedures of each type of measurement device.
1. Overview of the Series 📌
The CEN/TS 15901 series is prepared by the European Committee for Standardization (CEN) committee responsible for road and airfield surface characteristics; the UK participates through Technical Committee B/510/5. The series gives a separate procedure for each type of skid-resistance measurement device. The two parts in this batch are summarised below:
| Standard | Device | Principle | Year |
|---|---|---|---|
| PD CEN/TS 15901-14:2016 | ViaFriction (Road Analyser and Recorder ROAR of ViaTech AS) | Longitudinal Controlled Slip (LFCN) | 2016 |
| PD CEN/TS 15901-15:2014 | IMAG | Longitudinal Controlled Slip (LFCI) | 2014 |
⚠️ Different devices show systematic differences in their readings and cannot be directly converted or mixed. Engineering applications should state the device used and the corresponding part of the standard, and keep device consistency within the same measurement network to ensure comparable results.
2. Longitudinal Controlled Slip Measurement Principle 🔧
The basic principle of longitudinal controlled slip (LFCN/LFCI) devices is: the test vehicle travels at a constant speed while the test wheel maintains a predetermined longitudinal slip ratio (usually a fixed value) with the pavement surface; the longitudinal force on the test wheel is measured and combined with the normal load on the tyre to calculate the pavement friction coefficient (often denoted by a specific symbol such as the LFCN coefficient).
This type of method can continuously collect pavement anti-skid data while maintaining a relatively high travelling speed, covering a long distance in a short time and with high test efficiency. It is particularly suited to wide-area surveys of long road sections or airfield runways, and is also useful for before/after maintenance comparison, black-spot investigation, and trend analysis of anti-skid degradation.
✅ Compared with spot portable pendulum testers (e.g., BPN), the friction coefficient measured by a longitudinal controlled slip device is closer to the actual vehicle braking condition, reflecting the true tyre-pavement adhesion under longitudinal sliding.
3. Part 14: ViaFriction Device 🔩
PD CEN/TS 15901-14:2016 specifies the procedure for determining skid resistance using the ViaFriction device (the Road Analyser and Recorder ROAR manufactured by ViaTech AS). Its content covers the device construction, test wheel and tyre conditions, slip ratio setting, test speed, wetting (wet-state) control, data acquisition and processing, and result reporting format.
The standard requires defined test environment and vehicle conditions: testing under specified wet conditions (ensuring a wet pavement), travelling at the specified speed, with the test-wheel tyre size and wear state complying with requirements, and recording and, where necessary, correcting for influencing factors such as temperature, to ensure repeatability and reproducibility of the measured values.
⚠️ Device calibration and tyre condition are key factors affecting measured values. Test-wheel tyre wear, inflation pressure, tread pattern and equipment calibration all significantly alter the measured friction coefficient, so operation and verification must strictly follow the standard.
4. Part 15: IMAG Device 🔩
PD CEN/TS 15901-15:2014 specifies the procedure for determining skid resistance using the IMAG device. Like Part 14, IMAG also uses the longitudinal controlled slip principle (corresponding abbreviation LFCI), characterising anti-skid performance by measuring the longitudinal force at a predetermined slip ratio between the test wheel and the pavement.
This part likewise specifies device construction, test wheel and tyre, slip ratio, speed, wet-state control, data acquisition and result reporting, and provides its field of application and recommended uses, helping users judge the applicability of the device in different road and airfield scenarios.
5. Key Technical Requirements and Applications 📋
Combining the two parts, the key requirements for determining skid resistance include:
- Device consistency: test-wheel tyre size, inflation pressure, wear, tread and load must comply with requirements; the device must be calibrated and in good condition;
- Test conditions: test at the specified travelling speed and longitudinal slip ratio; for wet tests ensure the pavement is sufficiently wetted;
- Environment recording: record pavement temperature, ambient temperature, wind speed, etc., applying temperature correction where necessary to keep results comparable;
- Data quality: identify and reject anomalous readings and compute representative indices by road section;
- Result reporting: reports should state the device, standard part, test date, section, speed, slip ratio and statistical results, to support maintenance management decisions.
In engineering practice, these methods are widely used for: acceptance testing of new pavements, periodic testing of in-service pavement anti-skid performance, investigation of accident-prone sections, evaluation of winter de-icing and anti-skid strategies, and monitoring and safety assessment of airfield runway friction characteristics.
💡 Maintenance advice: when the measured friction coefficient falls below a management threshold or shows a clear downward trend, evaluate whether anti-skid restoration measures such as micro-surfacing, milling and resurfacing, or grooving are warranted, taking into account traffic volume, accident data and pavement structural condition.
6. Frequently Asked Questions ❓
❓ Q: Why are separate standard parts needed for different measurement devices?
A: Different manufacturers and principles differ in tyres, slip ratio, construction and data processing, so the measured anti-skid indices are not the same physical quantity. CEN/TS 15901 gives a separate part for each device, ensuring each measurement is repeatable and comparable.
A: Different manufacturers and principles differ in tyres, slip ratio, construction and data processing, so the measured anti-skid indices are not the same physical quantity. CEN/TS 15901 gives a separate part for each device, ensuring each measurement is repeatable and comparable.
❓ Q: What is the difference between LFCN and LFCI?
A: Both are longitudinal controlled slip measurements, but they correspond to the ViaFriction (LFCN) and IMAG (LFCI) devices respectively, with different abbreviations and value definitions. Use the symbols and definitions of the relevant part in practice.
A: Both are longitudinal controlled slip measurements, but they correspond to the ViaFriction (LFCN) and IMAG (LFCI) devices respectively, with different abbreviations and value definitions. Use the symbols and definitions of the relevant part in practice.
❓ Q: Why measure “wet-state” skid resistance?
A: Pavement friction drops markedly when wet, which is the main cause of wet-weather skidding accidents. Wet-state skid resistance better reflects real safety conditions, so anti-skid tests are usually carried out on a wetted surface.
A: Pavement friction drops markedly when wet, which is the main cause of wet-weather skidding accidents. Wet-state skid resistance better reflects real safety conditions, so anti-skid tests are usually carried out on a wetted surface.
❓ Q: How do continuous devices differ from a pendulum tester?
A: A pendulum tester is a spot measurement with low speed and limited representativeness; a longitudinal controlled slip device can measure continuously and at speed, covering longer sections with higher efficiency and closer to actual braking conditions, though device and calibration costs are higher.
A: A pendulum tester is a spot measurement with low speed and limited representativeness; a longitudinal controlled slip device can measure continuously and at speed, covering longer sections with higher efficiency and closer to actual braking conditions, though device and calibration costs are higher.
❓ Q: Can the measured friction coefficient be used directly as an acceptance threshold?
A: No single threshold should be applied directly. Each project should set its own threshold according to road class, speed, traffic composition and management requirements, while ensuring consistency of device, speed and temperature correction.
A: No single threshold should be applied directly. Each project should set its own threshold according to road class, speed, traffic composition and management requirements, while ensuring consistency of device, speed and temperature correction.