Trolleybus trials in Hong Kong

Hong Kong is known for streets full of air conditioned double decker buses, spewing diesel exhaust onto the crowded streets. But back in the 2000s bus operator Citybus tested something a lot cleaner – electrically powered trolleybuses.

TVB news report, June 2001

Trolleybuses existed before diesel powered buses, and are quite simple – they draw power from overhead wires (generally suspended from roadside posts) using spring-loaded trolley poles to power their electric motor. Unlike trams, they don’t need tracks and are able to manoeuvre around stopped vehicles. has a short summary of the trial:

Citybus first announced in March 1999 that they would invest HK$5 million to conduct a trolleybus trial, to study its feasibility for Hong Kong.

The trial involves two main elements: (1) the construction of a test track with an overhead wire network at the Citybus Wong Chuk Hang depot; (2) the conversion of a regular diesel bus into the world’s first double-deck air-conditioned trolleybus.

The trolleybus is converted from 701 (GD 1492), a 10.6m Dennis Dragon with a Duple Metsec body assembled by Caetano of Portugal. The roof structure had to be strengthened to take the extra load from the boom equipment and the brake resistors. As much as possible of the original bus had been retained.

But a government study found significant challenges to be resolved before their introduction:

Trolleybuses would be technically and operationally feasible in most circumstances in Hong Kong, but the feasibility of their operation in busy urban areas and in tunnels has yet to be established. There are important technical and operational issues to be resolved for trolleybus operation in these areas, in particular –

(i) trolley vehicles: the preferred vehicle type for Hong Kong is an air-conditioned, low-floor double-deck trolleybus. This new vehicle type would need to be designed. For manufacturers to be sufficiently interested to develop a new vehicle type, a minimum order of about 40-50 buses would be necessary;

(ii) vertical clearance: the recommended normal height for trolley wires is 6 metres. This exceeds the vertical clearance of many over-bridges constructed in accordance with Government standard clearance of 5.1 metres. There is a possible need for speed restrictions under this clearance in order to reduce the risk of dewirements. As for temporary structures and overbridges which provide Government standard clearance of 4.7 metres, the operation of double-deck trolleybuses would not be possible. Measures like temporary diversion, use of auxiliary engines, or temporary substitution by diesel buses would be required and these measures could be difficult and costly;

(iii) traffic impact: the constraint that trolleybuses could operate only within the reach of their trolley booms from the trolley wires, their inability to overtake one another without passing loops, and the possibility of dewirement would contribute to potential traffic delays especially in congested urban corridors;

(iv) depot location: trolleybus depots should be as close to the trolleybus network as possible to avoid the stringing of wires with no revenue-earning operation, thereby adding to the cost;

(v) hanging signs: repair or construction work on hanging signs directly above trolleybus wires (which, unlike tram wires, have both positive and negative overhead wires) would be dangerous. Legislation for relocating or removing such signs and compensation of owners would have to be considered;

(vi) fire-fighting: solutions have to be developed to prevent the trolley wires and traction poles from blocking the access of aerial ladders; and

(vii) infrastructure support: the planting of traction poles and underground feeder cables in busy urban areas could cause problems and solutions to them could be costly and time-consuming.

No single issue would stand in the way of trolleybus operation. However taken together they present important risks which would be greatest if trolleybuses were to be introduced in busy urban areas.

After the initial trials in 2001 little happened, an exception being a public display in 2003. The trolleybus itself was later stripped for parts, then scrapped in 2014.

Another video

Trolleybus at the Wong Chuk Hang test track.

Further reading

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9 Responses to Trolleybus trials in Hong Kong

  1. Myrtonos says:

    Let’s talk about the challenges claimed needed to be resolved:

    Trolleybuses would be technically and operationally feasible in most circumstances in Hong Kong, but the feasibility of their operation in busy urban areas and in tunnels has yet to be established.
    Not so as trolleybuses have been in service in many other cities for over a century, the feasibility of their operation has long been established. And trolleybus tunnels do exist in a few places. New Zealand’s capital, Wellington, has bus tunnels that were still used by trolleys until their abandonment quite late in 2017. Japan has two underground trolleybus lines too!

    (I) Trolley vehicles: No comment

    (II) Vertical clearence: See below

    (III) Traffic impact: Not generally so, trolleybuses don’t have to be in the lane under the wires. If there are three lanes each way, one pair of wires is enough that trolleybuses in any lane can draw power from them.
    If a trolleybus needs to pull over, stop and stay for a considerable amount of time, the poles can just be lowered and other trolleys can still pass.

    (IV) Depot location: This is valid for trams, right? And shouldn’t bus depots be as close to at least some bus routes as possible? In fact, newer trolleybuses have auxiliary power units and are capable of off-wire manoeuvres, so depots may not need to be wired.

    (V)Hanging signs I don’t see this myself, obviously, something like this must be done in cities that already have them.

    (VI) Fire-fighting: I don’t see why this is so and wonder if they already have solutions for tram wires.

    (VII) Infrastructure support: Surely not that much different from tram wires, and surely there are many places where trolleybus wires could just be supported from buildings.

    • It’s been 20 years since the Hong Kong trolleybus proposal was made, I don’t see why you’d bother with building a new trolleybus system these days – battery electric buses are now cheap and practical.

      • Myrtonos says:

        Not quite 20 years.

        The reason for building a new trolleybus system would be the same as the reason overhead power is still used on new tram installations, and still being installed on railways.

        Trolleybuses had already worked well for over a century when that trial was done, and someone proposed with a new trolleybus system back then and many were built decades earlier, yet.

        Note that rechargeable batteries have also been around for over a century, and in all that time, trolleybuses have generally been preferred over static electric buses.

        Note that all new trolleybuses do have batteries for off-wire manoeuvres, and as far as I know, trolleybus wires are still cheaper to install and move than tram tracks.

  2. A Meow Cat says:

    Is that ‘trolleybus’ in the picture a converted Leyland Olympian? Bears an uncannily resemblance to its Singaporean counterparts! (unfortunately the Singaporean vehicles were scrapped in 2011 so none of them exist but you can look them up on the web!)

  3. MATHEW K THOMAS says:

    Pure battery or trolleybus – it need not anymore be a this vs that tussle. The battery trolleybus is an ideal amalgam of both. Just lower the collectors in city centres, tunnels and under the bridges and run it on batteries. In Motion Charging will take over as soon as the bus is back under the wires again after a few kilometers. No need for expensive opportunity charging sub-stations, no need to “stand still” for charging. Overhead wire infrastructure is super simple too, only straight sections. Catenary absent at crossings, depot, turning loops, dense city areas. The battery is smaller and its life is longer due to better SoC/DoD management.

  4. I’m totally with Mathew Thomas and Myrtonos here. We need to get away from the “this vs that” approach. All over the world, transport operators need to start looking (properly) at the merits of in-motion charging, which benefits the trolleybus concept significantly. On many routes worldwide, the concept is a more flexible and cheaper option than rail transport. COVID has also weakened the economic justification for rail almost everywhere. The existing electrical supply can be repurposed to feed trolleybuses, especially at the outer ends of many rail commuter routes, where a road-based vehicle gives more flexibility. My advice would be – no more commuter rail construction anywhere. Think about that!

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