232.1 Clear gap targets

Set maximum passable width that blocks target vehicles while allowing mobility aids. Use vehicle baselines (322). HVM bollard arrays adopt this pass/fail, and a crash rated bollard maintains it after deflection/set (314).

Define the clear-gap target early using the site’s vehicle baseline and pedestrian needs. For hostile vehicles, the governing dimension is the minimum external width that can thread the line. For accessibility, preserve wheelchair/mobility-aid passage where intended routes exist. For crash-rated layouts, the clear gap must remain below the passable width after elastic deflection and permanent set (314).

When setting a target, reference your vehicle class shortlist (223) and confirm geometry at capture height (312). If your array protects an egress route, coordinate with 231 People Flow & Egress Widths. Record the value and basis in your VDA (221) so reviewers can reproduce the decision.

232.2 Edge cases (slopes/curbs)

Account for angle and level changes that change effective gap. Add vertical projection drawings. HVM bollard gaps on slopes need tighter nominal spacing; a crash rated bollard must include grade impacts in acceptance.

On ramps, crossfalls, and crown changes, the effective width between heads increases because the vehicle body approaches at an angle. Project the bollard heads onto a vertical plane aligned to the approach vector (225) and re-check the gap at capture height (312). On down-slope approaches, tighten nominal centres a few millimetres to compensate for the widening effect, and document the allowance in drawings and the assumptions register.

At curbs, measure from the drivable edge (back-of-kerb) and consider mountable profiles. For crash-rated systems, include grade in the SAT acceptance notes (638) and use a gauge shaped for the incline so evidence is unambiguous.

232.3 Corner & island treatment

Treat radii with staggered posts or islands (324). HVM bollard corners resist cut-throughs; ensure a corner crash rated bollard orientation matches certificate envelope (421).

Vehicles cut corners, so radii can open exploitable throats. Use staggered patterns or add a small corner island (324) to hold the gap. Where products have orientation-dependent performance (421), rotate posts to match the certified impact face for likely vectors (225). Validate with a vector diagram overlay (936) showing the swept envelope and residual gaps.

On multi-approach corners, blend two patterns and check both paths. Keep refuge pockets for pedestrians clear of vehicle desire lines and sign them with conspicuity/signal plans (353).

232.4 Near-door spacing

Prevent wing-doors and trolleys from snagging array heads (323). HVM bollard gaps widen locally for egress; the nearest crash rated bollard must still meet gap rules at full height (312).

Doors, glazing, and retail frontages often need slightly wider local spacing to prevent snagging and to pass trolleys. Use the door protection array guide (323) to shape these transitions without opening a passable vehicle throat. Maintain capture height and avoid low-head designs that can be climbed. For automatic lanes near entrances, coordinate modes of operation (525) so pedestrian egress isn’t blocked during alarms.

232.5 Adjacent walls/fences

Measure wall-to-post clearances and prevent climb/ramps. For HVM bollard runs, avoid funnel effects; when wall-post is a crash rated bollard, verify residual set doesn’t create a wider throat (314).

Between a wall/fence and the first post, keep the gap at or below the site’s pass/fail value. Protect against ad-hoc ramps by preventing debris accumulation and specifying end-stop details. Where alternating wall–post–post creates a funnel, insert an offset post to break the line of approach (214). For crash-rated runs, check that permanent set (314) after a hit does not widen the wall-side throat beyond your clear-gap limit.

232.6 Mixed-height arrays

Blend heights to prevent vehicle climb while preserving sightlines (316). HVM bollard mix rules include consistent gap at effective height; a lower crash rated bollard head may need closer centers.

Mixing heights can reduce climb-over risk and preserve sightlines, but you must hold the clear gap at the governing capture height. Where lower heads are needed near heritage frontages or signage (316), close the centres slightly so the projected opening at capture height remains below the pass threshold. Confirm that mixed heights don’t conflict with certification orientation or footing classes (421, 332).

232.7 Tolerance & installation drift

Stack fabrication/set-out tolerances (315, 612). HVM bollard drawings include worst-case gap; crash rated bollard acceptance checks use calibrated gauges (626).

Gap drift happens: tube OD tolerances, sleeve ovality, head concentricity, and on-site set-out all stack up. In the design, include a tolerance budget (315) and publish the worst-case clear gap on the drawing. During installation, follow 612 Setting-Out & Benchmarks and verify with 626 Datum & Alignment Checks. Capture measurements in the photo/redline log (937) so SAT witnesses can see the evidence trail.

232.8 Inspection gauges

Use rigid bars or step gauges sized to targets. Record pass/fail with photos (716). HVM bollard SAT includes gauge results; a crash rated bollard gauge accounts for deflection.

Prepare two tools: (a) a rigid go/no-go bar sized to the pass/fail width, and (b) a stepped gauge to check at capture height(s). For slopes, use a wedge-base gauge that matches the gradient so readings are fair and repeatable. During 638 SAT/Witness, log each location with a close-up plus a context shot following the 937 Photo/Redline Logbook. Store gauge calibration records with the 918 witness/inspection forms.

232.9 Worked spacing examples

Provide door, corner, and frontage examples with numbers (323–324). HVM bollard tables show nominal vs effective; pair with a crash rated bollard deflection allowance (314).

(a) Door frontage: Target clear gap = 1,100 mm for mobility aids; hostile pass threshold = 1,000 mm. Use three posts: centres 1,450–1,550 mm, but tighten by 20 mm each side where the approach is down-slope. Show a local transition back to the site-wide 1,200 mm nominal pattern; annotate capture height.

(b) Corner radius: For a 6 m outside radius, stagger two posts through the apex and add a 0.6 m island at the chord to prevent cut-through. Validate with a vector overlay and record effective gap on the chord line under likely angles (225, 324).

(c) Crash-rated set allowance: If certification or prior testing shows up to 40 mm permanent set at the head (314), deduct this from your nominal centres when calculating the post-impact effective gap. Include the allowance in the SAT acceptance band so disputes are avoided on the day.

232 Spacing rules for HVM & Crash-Rated Bollards — FAQ