User guide
Riding on difficult road surfaces on an e-scooter: contact-patch physics on cobblestones, tram tracks, gravel, wet leaves, painted lines and expansion joints
Six disciplinary micro-environments that no existing guide covers individually: cobblestones (Belgian setts, granite slabs, round river-rock cobbles — 5–30 Hz vibration, micro-loss-of-contact, μ_wet 0.3–0.4, sweet-spot speed, line between joints); tram tracks (wheel-slot 35–45 mm wide × 38–58 mm deep for standard 1435 mm gauge, crossing angle ≥45° mandatory, convex rail head, wet-rail μ 0.05–0.10 — worse than ice, four failure modes); gravel and sand (two-layer dynamics, front-wheel plowing effect, amplified slip-angle in cornering); wet leaves (μ ~0.1 as on ice); painted lines (μ_wet ↓ ×3 to 0.2–0.3, metal manhole covers and plates even worse); expansion joints and poor patch repairs (parallel-grooves like miniature rails, step-transitions deflecting the front wheel, sunken utility covers 2–5 cm below grade). The common denominator is the 5–15 cm² contact patch on an e-scooter tire and the three types of its failure: material μ failure, geometric trap-or-deflect, kinetic momentary contact loss from vibration. Defensive cross-cut: tire-pressure adjustment 30–35 PSI vs 40–45, active stance with soft knees and elbows for 2–3 cm of vertical absorption, weight bias (rear over bumps, forward over slick patches), 60–75 % of normal speed, rear-brake-first on slippery surfaces. Especially relevant for Ukrainian cities with cobblestoned historical centres (Lviv, Kyiv-Podil, Kamianets-Podilskyi) and tram networks (Kyiv, Lviv, Kharkiv, Dnipro, Odesa, Mariupol). ENG-first sources: Edinburgh/Vienna/Toronto tram-track cyclist injury studies, AASHTO/TRB pavement marking BPN friction standards, Paris-Roubaix vibration analysis (cycling-physics engineering refs), wheel-rail interface μ literature, Schwalbe/Vittoria tire pressure technical guides, ASCE bridge expansion joint design, OSM surface= + smoothness= tag refs, League of American Bicyclists wet-leaves safety briefings.