The Pole Height Formula
The classic rule: mounting height (H) = 0.6 × road width (W) to 0.8 × W. For a 7m wide road: H = 4.2m to 5.6m - use a 5m or 6m pole. For a 10m road: H = 6m to 8m - use a 7m or 8m pole. For a 14m dual carriageway: H = 8.4m to 11.2m - use a 9m or 10m pole with central or dual-arm installation. The inter-pole spacing (S) should be 3 × H to 4 × H for good uniformity. Example: 6m pole → 18m to 24m spacing. Tighter spacing with shorter poles can work for narrow lanes.
Pole Height by Road Category
Village lane (3m wide): 4m pole, 20m spacing, single arm. Colony road (5–6m): 5–6m pole, 20–25m spacing. Municipal road (7–8m): 6–7m pole, 25–30m spacing. State highway (10–12m): 8–9m pole, 30m spacing, staggered. National highway (14–16m): 10m pole, 35m spacing, central median or dual arm. Industrial access road (6–8m): 6–7m pole, 25m spacing. Garden path (2m): 3–4m decorative post, 10–15m spacing. Parking lot: 8–10m pole with 90° flood beam, 20m grid.
The Effect of Height on Glare
Glare (direct view of the light source) is a safety issue - it temporarily blinds drivers. Higher mounting height generally means the light source is further from the driver's line of sight, reducing glare. However, very high poles with wide beam optics can still cause glare if the luminaire is not properly shielded. The ULOR (Upward Light Output Ratio) should be 0% for road lighting - light should go downward and sideways only, not upward (which causes glare to oncoming traffic and light pollution).
Pole Overhang (Arm Length)
The overhang is the horizontal distance from the pole centreline to the luminaire. Standard overhang: 0.5m (pole is at road edge, light is over the edge of the road). Extended overhang (1.5–2m): used when the pole cannot be placed at the road edge (obstruction, footpath). Longer overhang creates more bending moment - requires a stronger, thicker pole arm and larger pole base plate. For 9m poles with 2m overhang in wind zone 3 (most of inland Maharashtra): confirm structural adequacy with the pole manufacturer's load table.
