Music fans are upset with a "no re-entry" rule introduced this year at St Jerome's Laneway Festival Singapore.

The new policy means festivalgoers cannot exit and re-enter the festival grounds at Gardens by the Bay for the entire duration of the outdoor concert, which is scheduled to run tomorrow from 10am to about midnight.

So, if this year's crowd is the same size as last year's, about 13,000 music fans could be jostling for space over 12 hours in the festival grounds at The Meadow, which spans about 22,000 sq m, or three football fields.

Of course, not all ticket holders will be attending the event from start to finish, but previously, they could come and go, depending on when their favourite acts were scheduled to perform.

Explaining the "no re-entry" decision, organisers cited issues of "safety and security, especially in view of recent incidents at other festivals around Asia", in a post on the event's Facebook page.

Citing festivals in Australia, where the "no re-entry" rule is common, festival director Matthew Lazarus-Hall says: "Part of it has to do with safety and security and providing festivalgoers with a safe and fun environment."

He adds that the organisers decided to implement the new ruling after an internal assessment.

To help festivalgoers cope with the rule, Laneway Singapore said on Facebook that there will be an extended perimeter and "more than one air-conditioned tent onsite" for fans to chill out in.

Additionally, instead of having to purchase tokens, festivalgoers can use cash or credit card to pay for all food and drinks.

However, the "no re-entry" rule is still a sore point with some punters. Ms Alicia Ali, 28, a public relations consultant who has attended four Laneway Festivals in Singapore, says the rule inconveniences concertgoers.

She says: "My entire group of seven people will be going in only at 4 or 5pm to catch the main acts because we don't want to stay so many hours in the grounds."

For past editions of the festival, she and her friends would join the event at about 2pm and then leave in the mid-afternoon to take a break, before returning in the evening to catch the bigger acts.

While she has attended other overseas festivals which do not allow re-entry - including Stereosonic in Australia and mega electronic dance music festival Ultra Europe - those were held in grounds that were considerably larger.

She adds: "Those were entire self-sustaining cities on their own. Food and beverages were cheap and there were places for concertgoers to go to chill out."

A Facebook user by the name Rhiannon Alyse Young, who will be attending this year's Laneway, supports the rule change, saying: "You've spent good money on a ticket, why not make the most of the day? Go and have a drink or something to eat, wander around, hang out with your mates, maybe go and see a set of someone you don't know, you might find new bands/artists that you like."

Laneway Singapore said on Facebook that the "no re-entry" rule "has been stated on the website and ticketing page since the start of ticket sales".

The FAQ section of the website adds that "Laneway Festival is well stocked with food and drinks and equipped with sufficient portaloos, first aid stations and other necessary amenities onsite".

Other large-scale outdoor events held here include beach dance music festival ZoukOut on Sentosa in December and the Formula One Singapore Grand Prix in the heart of the city in September. Both events allow their patrons to leave and re-enter the grounds.

Zouk's head of marketing and events, Ms Sofie Chandra, 32, says the "no re-entry" rule has been implemented at many concerts and festivals overseas.

But ZoukOut, a two-day beach festival which drew 45,000 people last year, decided not to introduce the "no re-entry" rule.

She says: "We believe our consumers have been used to enjoying the freedom of re-entry at ZoukOut and we see it as a value-add and part of the customer experience for them."

Singapore GP executive director Michael Roche, 58, explains that allowing re-entry is a costly affair, requiring "a huge amount of manpower to have exit gates running and additional security to re-check and re-screen people".

He adds: "Security costs are very high and those are passed on to the customer.

"Every event organiser has to decide whether it wants to do it or not. There's no right or wrong answer."

Laneway ticket prices have seen an increase of almost 10 per cent - from last year's $165 to this year's $180 for standard tickets.