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PD 06634 — Vehicle Restraint Systems (Roadside Barriers and Bridge Parapets) Technical Document Series
Vehicle Restraint Systems — Fundamentals, Highway Barriers, Bridge Parapets, Transitions and Crashworthy Roadside Features (1999)
📐 PD 06634 is a series of BSI Published Documents under the collective title “Vehicle restraint systems”. Prepared by Subcommittee B/509/1 (Road restraint systems) of Technical Committee B/509 (Road equipment), all six parts came into effect on 15 October 1999. The series consolidates more than thirty years of research, testing, design, specification and standardisation work carried out by the Department of the Environment, Transport and the Regions (DETR), the Transport Research Laboratory (TRL), BSI and other organisations on vehicle restraint systems such as safety fences, barriers and bridge parapets. As Published Documents rather than British Standards, the parts do not carry the force of mandatory requirements; nevertheless, the database and the engineering principles they contain remain an authoritative reference for the selection, design, qualification and acceptance of road restraint systems in the UK and across Europe.
💡 PD 06634 works best as a “knowledge base” rather than a mandatory design code. It gathers the geometry, performance, testing and historical development of barriers, terminals, transitions and bridge parapets into one place, and is routinely used alongside BS EN 1317 (the European road restraint systems standard) when engineers compare options and prepare compliance statements.
1. Scope and Overview of the Series 📌
PD 06634 comprises six parts covering the full knowledge chain of vehicle restraint systems, from the fundamental database, through the physics of highway restraint systems and the development of UK barriers and bridge parapets, to transitions, terminals and crashworthy roadside features:
- Part 1: Fundamentals — Database: fourteen summary tables set out details of untensioned corrugated beam (UCB), concrete safety barriers (CSB), wire rope safety fences (WRSF), tensioned corrugated beam (TCB), open box beam (DHOBB/SHOBB), transitions and connections (TRNCX), barrier terminals (TERM), rectangular hollow section (RHS), combined parapets (PCOMB), metal parapets (PMET), concrete parapets (PCONC), masonry vehicle parapets (PMAS), arrester beds/crash cushions/removable features (REM) and computer models (MODL).
- Part 2: Fundamentals of highway restraint systems: economic justification for safety barriers, controlled vehicle impact testing, test vehicle propulsion and steering control, measurement of vehicle and restraint system test data, vehicle stability and barrier characteristics, and impact severity indices such as THIV, PHD, ASI, OIV, RDA and VIDI.
- Part 3: Development of vehicle highway barriers in the United Kingdom: post and rail barriers, the blocked-out beam barrier (BOB), untensioned corrugated beam (UCB), wire rope safety fence (WRSF), tensioned corrugated beam (TCB), tensioned rectangular hollow section (RHS), open box beam (OBB), and concrete safety barriers (BCB, VCB, HVCB and their temporary versions).
- Part 4: Development of bridge parapets in the United Kingdom: vehicle parapets for bridges, their containment and historical development.
- Part 5: Development of barrier transitions and terminals: connections between different barrier types (TRNCX) and safe end treatments (TERM).
- Part 6: Crashworthy roadside features — Impact attenuators: energy-absorbing crash cushions, arrester beds, sand/wood barriers and other sacrificeable features.
⚠️ Parts 4, 5 and 6 of PD 06634 are based on scanned copies; the descriptions of those parts in this article are written from publicly available domain knowledge for background and technical context. Dimensions, performance values and acceptance requirements should always be confirmed against the current official BSI publications and the BS EN 1317 series.
2. Series Structure and Technical Essentials 🔧
The table below maps each part of the series to its core subject matter so that engineers can quickly locate the documentation they need.
| Part | Subject | Core Technical Content |
|---|---|---|
| Part 1 | Fundamentals — Database | 14 summary tables: UCB, CSB, WRSF, TCB, box beam, TRNCX, TERM, RHS, PCOMB, PMET, PCONC, PMAS, REM and MODL |
| Part 2 | Fundamentals of highway restraint systems | Economic justification, controlled impact test criteria, propulsion and remote steering, data measurement, impact severity indices (THIV/PHD/ASI/OIV/RDA/VIDI) |
| Part 3 | Development of vehicle highway barriers in the UK | Post and rail barriers, BCB/VCB/HVCB concrete barriers, TCB, RHS, OBB and temporary barriers |
| Part 4 | Development of bridge parapets in the UK | Vehicle parapets for bridges: construction, containment levels and evolution |
| Part 5 | Development of barrier transitions and terminals | Transitions (TRNCX) between different barrier types and terminal (TERM) end treatments |
| Part 6 | Crashworthy roadside features — Impact attenuators | Crash cushions, arrester beds, sand/wood barriers and sacrificeable end features |
3. Key Technical Requirements and Evaluation Indices 🔥
Although presented as a document and database series, Part 2 systematically sets out the principles of evaluating highway restraint systems, which remain central to modern crash-safety assessment:
- Economic justification: Part 2 builds the economic and safety case for no median barriers, median barriers, verge barriers on motorways and all-purpose roads, and higher containment barriers on motorways.
- Controlled vehicle impact testing: test criteria, standard controlled barrier impact test conditions, and the relationship to the European standard for road restraint systems (BS EN 1317).
- Data measurement: photography, vehicle instrumentation, measurement of the vehicle centre of mass, test reporting, plus vehicle propulsion and remote steering control.
- Impact severity indices: THIV (theoretical head impact velocity), PHD (post-impact head deceleration), ASI (acceleration severity index with ellipsoidal envelope), OIV (occupant impact velocity), RDA (ride-down acceleration) and VIDI (vehicle interior deformation index) quantify occupant injury potential.
- Strong and weak post concepts: Clause 6 discusses strong and weak post barriers, factors leading to spinout, lateral deceleration, overturn stability, impact force and energy absorption.
🚨 Restraint system safety must never be judged by appearance or mounting height alone. PD 06634 stresses that severity indices such as ASI and THIV are the core quantitative evidence of “occupant-friendliness”; any newly developed barrier, transition or terminal must pass controlled impact testing and produce a complete test report.
4. Engineering Practice and Application 🛠️
In practical highway and bridge engineering, PD 06634 is valuable in the following respects:
- 🔍 Option comparison: the 14 summary tables of Part 1 allow rapid comparison of corrugated beam (UCB/TCB), wire rope (WRSF), concrete (CSB/BCB/VCB), box beam and RHS barriers in terms of geometry and performance.
- 🔧 Bridge interfaces: bridge parapets (Part 4) differ greatly in stiffness from roadside barriers; transitions (TRNCX in Part 5) are needed to smooth the connection and prevent vehicle snagging, spitting or under-ride.
- 📊 End safety: barrier terminals (TERM) and hazards ahead of barriers should be protected with crash cushions or other attenuators (Part 6) to reduce the lethality of head-on impacts.
- 📋 Regulatory linkage: PD 06634 connects with BS EN 1317 (road restraint systems), BS 6579 (safety fences and barriers for highways) and BS 6779 (highway parapets for bridges). In modern practice, containment and performance classes of BS EN 1317 are the mandatory basis, while PD 06634 serves as the historical and technical supplement.
5. Frequently Asked Questions ❓
❓ Q: What is the relationship between PD 06634 and BS EN 1317?
A: PD 06634 is a BSI Published Document that systematically records the UK database, principles and development history of vehicle restraint systems, while BS EN 1317 is the European product and testing standard (adopted in the UK) that defines containment classes, performance classes and test methods. They are complementary: mandatory design relies on BS EN 1317; technical background and history come from PD 06634.
A: PD 06634 is a BSI Published Document that systematically records the UK database, principles and development history of vehicle restraint systems, while BS EN 1317 is the European product and testing standard (adopted in the UK) that defines containment classes, performance classes and test methods. They are complementary: mandatory design relies on BS EN 1317; technical background and history come from PD 06634.
❓ Q: Can the 14 tables of Part 1 be used directly for design?
A: The summary tables present engineering details and database information for barriers, terminals and transitions, serving as reference material for option selection and specification; they are not the sole design basis. Geometry, materials and performance must still reference the appropriate product standards and BS EN 1317.
A: The summary tables present engineering details and database information for barriers, terminals and transitions, serving as reference material for option selection and specification; they are not the sole design basis. Geometry, materials and performance must still reference the appropriate product standards and BS EN 1317.
❓ Q: What do THIV and ASI mean to an engineer?
A: They quantify the injury potential of an impact to vehicle occupants. ASI (acceleration severity index) reflects the overall acceleration level experienced by occupants; THIV (theoretical head impact velocity) reflects how severely the occupant’s head would strike the vehicle interior. They are core pass/fail criteria in barrier crash tests.
A: They quantify the injury potential of an impact to vehicle occupants. ASI (acceleration severity index) reflects the overall acceleration level experienced by occupants; THIV (theoretical head impact velocity) reflects how severely the occupant’s head would strike the vehicle interior. They are core pass/fail criteria in barrier crash tests.
🔍 Q: Why do barrier terminals and transitions need special treatment?
A: A plain terminal is a rigid head-on surface that can be penetrated or cause extreme deceleration in a frontal crash; connecting barriers of different stiffness without a transition creates a stiffness step that destabilises vehicles. Parts 5 and 6 address transitions (TRNCX), terminals (TERM) and crash cushions precisely to defuse these danger points.
A: A plain terminal is a rigid head-on surface that can be penetrated or cause extreme deceleration in a frontal crash; connecting barriers of different stiffness without a transition creates a stiffness step that destabilises vehicles. Parts 5 and 6 address transitions (TRNCX), terminals (TERM) and crash cushions precisely to defuse these danger points.