Cat and dog owners will soon be able to bring pets on board the light rail on weekends and public holidays once the MTR Corporation rolls out a HK$99 monthly pet pass from May as part of a trial scheme.

Under current regulations, only guide dogs are allowed on trains.

The two-month pilot scheme will require owners to board the light rail with pets as long as they are kept in a bag that complies with luggage restrictions.

Bags with a single side that exceeds 130 centimetres or having a total dimension of more than 170cm would not be allowed.

“Passengers also need to board or get off from a specific location of the train,” said Cheris Lee, who heads the corporation's operating and metro segment, on Tuesday.

"That's the last train door of the light rail car.

“Please stay within that area... so that we can also maintain a proper, comfortable environment for other passengers as well,” she added.

The Society for the Prevention of Cruelty to Animals (SPCA) advised owners to take extra care of their pets to minimise stimulation and stress.

“We have to introduce the bag to the pet in advance,” said Lily Leung, senior behavioural support technician at SPCA.

"We advise the pet owner to do more introductory exercises at home so that your pet likes, or even loves, staying in the bag."

She added that a container with good ventilation and a size large enough for pets to turn around without restrictions is needed for a comfortable journey.

Leung also said owners should be alert for any signs of heatstroke in pets such as vomiting, panting and excessive drooling.

The MTR Corporation said the scheme is aimed at promoting an inclusive community.

It called for pet owners and other passengers to be considerate of each other so the scheme can run smoothly.

The trial period, it added, might be extended to collect more data, namely the number of pet passes sold, passenger behaviour and impact on the railway system.