Instead of just viewing estimated bus arrival times, commuters at 30 bus stops in Orchard Road and the Central Business District have been getting live updates on the number of donors required this month to meet the nation's needs.

The Singapore Red Cross (SRC) hopes these bus-stop digital ads will remind people that the need for blood does not stop even during this holiday period.

According to the SRC, experience has shown that blood collection in December can plunge by as much as 20 per cent across all blood types. This is because donors are usually busy with festive preparations or travelling during the school holidays.

Every day, 400 units of blood are needed by all hospitals for patients requiring blood transfusions for a variety of reasons, such as leukaemia, haemophilia and bleeding disorders. The SRC strives to maintain at least six days' supply of blood at any one time.

"In anticipation of the dip in collection, SRC has stepped up efforts to remind people to give the gift of life during the holiday season," said Ms Elaine Tham, head of the blood donor recruitment programme at SRC, calling the move "unprecedented".

Real-time data on the number of blood donors visiting the four blood banks in Singapore are being aggregated and the interactive digital advertisement panels that have been up since the first week of this month show the updated number of donors still needed for the month. At 6.30pm yesterday, 11,500 donors were still needed to meet this month's target.

The ads, which will be up till next Sunday, also prompt people to download the Red Cross Connection app which alerts users when blood stocks run low or when a specific type is needed urgently.

The ads are placed at bus stops in the heart of town because the blood bank nearby at Dhoby Ghaut has been popular with shoppers, office workers and students. The downtown blood bank contributed a fifth of the national supply last year. Last month, it expanded by incorporating the adjacent shop unit. This move enables it to collect 25 per cent more blood - 100 units instead of the previous 80 each day.

Student Ferlyn Tan, 19, was shopping at Dhoby Ghaut last week when she chanced upon the digital ad. "The live number update helps me to visualise exactly how many more donors are needed now and it prompted me to want to walk in to donate but I couldn't as I have just done so recently," she said.

Besides the digital panels project, the Red Cross also sent out postcards and magnets to over 77,000 households situated near blood banks to remind people to donate blood before the holidays.

Compared to a decade ago in 2004, the donor pool has grown by 40 per cent to 68,868 last year.

However, a greying Singapore also means more people are likely to need transfusions in the future.