222.1 Defining run-up

Run-up is unobstructed distance a vehicle can accelerate along a credible path (214). It sets HVM bollard tier demands and the crash rated bollard speed class (413).

In plain terms, the run-up distance is the usable length a hostile vehicle can exploit before reaching the intended impact point. Map this on site, not just in CAD, because kerbs, street furniture, and human “desire lines” change the true path.

The run-up you confirm here drives whether an HVM solution is justified versus a low-speed measure. It also frames the relevant rating class you must evidence (e.g., vehicle type, speed band).

222.2 Measuring real-world run-up

Measure kerb-to-door routes, corner cuts, and service lines with GIS/tape. Validate against time samples (224). Accurate run-up prevents oversizing HVM bollard arrays and mismatching a crash rated bollard certificate.

Start by marking the likely run-up corridor from the nearest acceleration point (e.g., a straight segment) to the frontage protection line. Measure centreline distance and any corner-cut shortcuts. Where sightlines or traffic flows force a deviation, trace the actual path vehicles take during busy periods.

Ground-truth with simple video time-samples during the 211 walkdown: record traversals and compare to Speed Estimation Methods (224). This reality check catches optimistic CAD assumptions and improves confidence in the final VDA inputs.

222.3 Obstacles and friction

Account for speed humps, paving type, and furniture (227). Friction reduces achievable speed, affecting HVM bollard density and permissible crash rated bollard rating.

Catalogue obstacles that sap speed: humps, cushions, raised crossings, tight bollard rows, trees, kiosks, and queue barriers. Note the traffic-calming type and spacing. Surface materials matter too—rough setts, loose sand, or soft asphalt have higher rolling resistance than smooth concrete, meaning a shorter distance is needed to shed speed.

In your VDA sheet, flag a conservative surface friction assumption and trace it to photos in the Evidence Capture Standards (716). Where friction is uncertain (e.g., seasonal sand), test again after cleaning or rain to bracket variability.

222.4 Traffic-calming effects

Existing chicanes/islands shorten effective run-up; temporary measures can too (239). Use them to reduce HVM bollard counts; still keep a crash rated bollard within tested limits (421).

Where chicanes, splitter islands, or narrowings are present, the effective run-up is often much shorter than the straight-line map suggests. Document the sequence and spacing of features, and simulate a realistic weave path. If you can introduce reversible event-mode measures (239), note their setup time and stewardship, then re-run the speed check to quantify the benefit.

Always confirm the chosen product remains within its rating-critical dependencies (421)—e.g., minimum approach angle, array geometry, and foundation class—so the calming you rely on doesn’t invalidate certification scope.

222.5 Gradients and surfaces

Downhill boosts speed; uphill and rough surfaces reduce it. Capture with photos and notes (716). These shift HVM bollard spacing and crash rated bollard selection (413).

Gradients act like a constant acceleration (downhill) or deceleration (uphill). Record the slope percentage over the key segments of the run-up corridor and tag them in your photo log (716). Combine slope with surface condition (wet, sanded, polished) to bracket the likely approach speed range rather than a single value.

If the downhill gain pushes speeds into a higher tier, consider redistributing the array and spacing or moving the line of protection to a flatter section, ensuring the selected rating in How to Read Ratings (413) still applies.

222.6 Turning radii influence

Tight radii lower speed; wide radii allow faster entries (324). Shape HVM bollard pattern at corners and confirm crash rated bollard orientation remains valid (225, 421).

Approach speed is strongly constrained by the corner geometry immediately upstream of the array. Small turning radii force lower speeds; generous radii and flared entries allow higher speeds. Reference the site’s Corners, Islands & Pinch Points (324) when testing alternative corner treatments that also preserve emergency access.

Where the credible path changes the approach vector, verify the product’s test orientation and the array’s capture width against Impact Angles & Approach Vectors (225) and the product’s as-tested configuration constraints (421).

222.7 Vehicle acceleration basics

Use simple distance–acceleration models with conservative margins (224). Resulting speeds map to HVM bollard tiers and crash rated bollard energy equivalence (414).

For planning, a simple constant-acceleration model over the usable run-up, clipped by practical limits (gear changes, steering input, friction), is adequate. Feed your measured distance, gradient sign, and a conservative acceleration into the VDA Approach-Speed Helper (922) and cross-check with Speed Estimation Methods (224).

Translate the resulting approach speed to the target rating band using Standards Equivalency (414) if needed. Document assumptions and a small safety factor to cover variability.

222.8 Evidence capture on site

Mark start/stop points, sightlines, and obstructions on photos/plans (716, 936). Evidence shortens review for HVM bollard choices and crash rated bollard claims (938).

Use the Photo/Redline Logbook (937) to annotate run-up starts, corner cuts, conflict points, and speed-reducing features. Add short video clips with timestamps for time-sample validation. Keep filenames aligned to the File Index & Naming Rules (911) so reviewers can follow the chain quickly.

Bundle the annotated images and VDA sheet entries into the Submission-Pack Guidance (938). Clear evidence reduces debate and helps authorities or clients trust the selected tier.

222.9 Documenting limits

Note enforcement, peak traffic, or barriers that limit hostile acceleration (351). These justify lighter HVM bollard solutions or a lower crash rated bollard band—with rationale (444).

Where operational controls (e.g., speed enforcement, staffed checkpoints, hard gates) reliably constrain acceleration, log them as rating-relevant context in the Evidence & Documentation (444). Include maintenance policies for any temporary or event-mode measures so the run-up constraint isn’t just theoretical.

Cross-reference the Hazard Analysis (351) to show your assumptions don’t introduce new risks (e.g., queue spillback into live traffic) and that the array still meets clear-gap rules.

222 Approach / Run-Up Distance — FAQ