Heritage trails have become more popular in recent years, and the slots for these walks can be filled up pretty quickly.
Despite their growing popularity, however, some organisers have reported a worrying trend - a rising number of no-shows.
Mr Kwek Li Yong, founder of civic group My Community, which runs three free tours a month in Queenstown, said attendance had fallen, dropping from 85 per cent in 2009 to as low as 60 per cent.
"People are defaulting on their online reservations. For some tours, we might have 80 people signing up, but just half showing up," he said.
A small number of those who drop out do use the group's online booking system to cancel their applications. However, most of the no-shows ignore the group's reminder e-mails, or reply only an hour ahead to indicate that they will not be turning up, said Mr Kwek.
Geylang Serai's Integration and Naturalisation Champions Committee, which organises heritage trails in the estate, said its worst no-show incident was in February. Just three of the 12 applicants showed up for a trail covering sites such as the former Geylang Fire Station in Paya Lebar and the former Queen's Theatre in Guillemard Road.
Some popular heritage trails
COMMONWEALTH AND HOLLAND VILLAGE
Launched in March and conducted on the third Sunday of each month, the tour traces the evolution of Queenstown's social history - from a rubber plantation in the 1870s to a military village, before it became an area for expatriates. It covers areas such as Chip Bee Gardens and the Ridout and Holland Park conservation area.
TIONG BAHRU HERITAGE WALK
This walk, which takes place on the first weekend of each month, is usually well subscribed. It is run by a team of 10 active volunteers and covers the pre-war and post-war architecture of the charming conservation housing estate.
The walk includes an exclusive visit to Singapore's first communal civilian air raid shelter in a residential estate, which helped to save lives during World War II.
BIDADARI HERITAGE TRAIL NATURE WALK
Officially launched last month, this trail takes participants through an area soon to be resigned to history.
It covers the Bidadari Memorial Garden, home to gravestones of those of various religions and ethnic groups, as well as the Mount Vernon Columbarium. These are slated to be cleared to make way for residences in the next few years. The next guided trail will take place on Sunday.
Committee chairman Lee Hong Ping said the tour was held despite the small turnout. He said those who went on the trail appreciated being in a small group as they got more in-depth explanations.
Organisers said that not turning up after signing up is a waste of valuable resources.
Mr Kwek said: "My Community's heritage tours are the fruit of our volunteers' labour. Each tour takes almost two years of preparation."
He said the preparations included purchasing licences for old images and conducting oral history interviews. They also included getting approvals from the authorities to gain access to restricted sites. Guides had to be trained as well. The civic group, a registered charity, has spent nearly $60,000 on organising these free tours, which run between three and four hours.
In response to queries from The Straits Times, a spokesman for the National Heritage Board (NHB) said that, even though guided trails at this year's Singapore HeritageFest were well-subscribed, with an average attendance rate of 80-100 per cent, there were cases where participants signed up for multiple free tours that overlapped.
She said this "denies others the opportunity to experience the tours".
The spokesman for Tiong Bahru Heritage Volunteers, a group that runs 2½-hour walks in the Tiong Bahru conservation estate free of charge, said that, while their events have seen rising turnouts, they understand that generally free heritage tours are often the hardest hit by no-shows as dropouts do not incur any monetary loss.
The longer lead time between registration and the actual event might also contribute to a higher dropout rate, he noted.
He said: "People might have signed up at a time when their schedules were still uncertain. Then, when other things came up, the first activities to give up would be the free ones."
That is why registration for Tiong Bahru heritage walks opens only two weeks before the event, he said.
The NHB spokesman said that, because many Singapore HeritageFest programmes are led by community volunteers, the board "hopes that participants will exercise responsibility in turning up for the programmes they sign up for".
My Community's Mr Kwek said: "The onus lies on the participants to reply to our reminders, to inform us that they are unable to attend the tours, so that we can forward their tickets to the hundreds on the waiting list."