Chapter 8 Roadworks Calculator – UK Traffic Management by IRSS

Instant UK roadworks setting-out distances: sign siting, taper length, cone counts and safety zones per the Red Book and Chapter 8.

Chapter 8 Roadworks Calculator gives street works and traffic management operatives instant setting-out distances for static roadworks in the UK – right in your browser toolbar. Choose the road type and permanent speed limit, enter the width and length of your works, and the calculator returns every minimum distance and equipment count from the "Safety at Street Works and Road Works – A Code of Practice" (the Red Book), which applies the principles of Traffic Signs Manual Chapter 8. WHAT IT CALCULATES • D – distance from the first "Road works ahead" sign to the start of the lead-in taper (metres and yards for distance plates) • Minimum clear visibility to the first sign • T – lead-in taper length for the total width of works including the sideways safety zone • S – sideways safety zone and L – longways clearance for the speed limit • C – clearance to the works vehicle • 45° exit taper and E – distance from the last cone to the "End" sign • Approximate total site length • Minimum cones for the lead-in taper, longitudinal run (9 m maximum spacing) and exit taper • Warning lights for the lead-in taper, minimum cone height and minimum sign size BUILT FOR THE REAL WORLD • Single carriageways from 20 to 60 mph and all-purpose dual carriageways up to 40 mph • Two-way traffic control mode (portable signals, Stop/Go, priority) with a 45° lead-in taper • Reduced 45° taper option for congested roads at 30 mph or less, with risk-assessment reminders • Darkness / poor visibility mode that flags when warning lights are mandatory • Clear warning when a road is outside Red Book scope (dual carriageways at 50 mph or more) and needs Chapter 8 design • Live layout schematic showing D, T, L, exit taper and E • One-click "Copy summary" to paste into a briefing, method statement or site WhatsApp group • Remembers your last inputs, works offline, light and dark mode HOW TO USE 1. Click the cone icon in your Chrome toolbar. 2. Select single or dual carriageway and the permanent speed limit. 3. Enter the works width and length in metres. 4. Tick any options that apply – two-way control, reduced taper, darkness. 5. Read off your distances and cone counts, or press "Copy summary". PRIVACY FIRST No accounts, no tracking, no data collection. Every calculation runs locally in your browser. IMPORTANT This is a guidance tool. All figures are minimums for static works. Always follow your site-specific risk assessment, the full Code of Practice and Chapter 8, and use trained, accredited operatives. A revised Code was published for consultation in 2026 – check you are working to the current edition. Not affiliated with the Department for Transport.