Horizontal Curvature
A. 19
A.20
A.21
The ability to negotiate small radius curves is a major advantage of LRT compared with conventional rail rapid transit systems. The exploitation of this ability does however impose certain penalties in terms of journey speed and vehicle design.
The existing Hong Kong tramway incorporates sone curves that by world standards are exceptionally tight (11-13 metre radius). Modern LRV's can be designed to negotiate such. tight curves, but this imposes a major constraint on design resulting in short, low capacity, expensive vehicles. Most light rail vehicles are therefore designed to negotiate curves of minimum radius of around 14-18 metres which has been found acceptable by most LRT systems. Curves of less than 18 metre radius on the existing tramway were therefore examined in order to determine whether they might be eased to this radius. Most of these tight curves were found to be at termini where new layouts. would in any case be desirable for the new longer cars; the adoption of a double-ended design facilitates their replacement.
The only tight curves found on main running tracks are at the junctions of Hennessy Road with Percival Street and Tin Lok Lane (both of which would cease to be used with the closure of the Happy Valley Loop) and at Western Market where realignment of the tracks to ease the curves is proposed. It is therefore recommended that new cars should be capable of negotiating horizontal curves of 18m. radius, though the ability to negotiate curves of 15-16m. radius would be desirable.
Gradients
A.22
The ruling grade used in the design of the system is 5 per cent. This is within the capabilities of nearly all modern LRV's, and steeper grades than this are found on many existing systems. However the ramp to surface for the westbound track from Pedder
85