Leaving enough space gives you time to react when the vehicle ahead slows or stops. For an HGV, the gap must reflect the vehicle, visibility and road conditions; a two-second count is not a guarantee that a heavy vehicle can stop safely.
What the Highway Code says
Rule 126 calls for at least a two-second gap on high-speed roads and in tunnels where visibility is reduced. At least double the gap in wet conditions; icy roads can require up to ten times as much. Large vehicles need more stopping distance. The rule gives a four-second gap for a large vehicle in a tunnel. See Highway Code Rule 126.
How to judge the gap
Choose a fixed point beside the road and count the time between the vehicle ahead passing it and your vehicle reaching it. Use this to notice when the gap has closed, then allow the greater distance your vehicle and conditions require. Reassess after speed changes or another vehicle moves into the space.
Look beyond the vehicle immediately ahead
Watch for slowing traffic, bends, junctions and reduced visibility. Keep enough clear road to stop safely. Do not rely on an unsourced stopping-distance figure for a loaded HGV: speed, road surface, gradient, tyres and braking condition all matter.
If another driver follows too closely
Stay calm, avoid sudden or retaliatory braking, and preserve room ahead so you can slow smoothly. Do not speed up beyond a safe or lawful speed because another driver is close behind.
Hazard lights are not a general signal to a tailgater. Under Rule 116, using them while driving is limited to warning following traffic of a hazard or obstruction ahead on a motorway or unrestricted dual carriageway, and only for long enough for the warning to be noticed. Read Highway Code Rule 116 for the full conditions.
Space in rain, ice and tunnels
Increase the gap before the conditions require abrupt braking. Spray and darkness can reduce the distance you can see to be clear. Follow tunnel signs and instructions as well as the spacing guidance; if stopped in a tunnel, Rule 126 specifies at least 5 metres to the vehicle ahead.
Driver assistance does not replace observation
Know the limits of any fitted assistance system and follow its operating instructions. Continue to judge the road, visibility and space yourself. A warning or automated intervention cannot guarantee that a collision will be avoided.
Prepare the rest of the journey
Following distance is one part of safe operation. Use our HGV safety guide for official sources on walkaround checks, loading, speed limits, fatigue and breakdowns.
Guidance checked against the Highway Code on 7 September 2026.