ASK him to recite the number plates of all the buses on route 51, and he reels it off.

Mr Joseph Lim, 32, is, in his own words, a bus fanatic. And the project manager is not alone in his obsession with buses.

He belongs to a circle of bus enthusiasts, estimated to number as many as 180. The informal group meets online via forums for bus enthusiasts.

Said Mr Lim, after reciting the registration numbers: "I don't make an effort to memorise the numbers. I love the buses so much, and look at them so much, the information gets into my subconscious."

A check with SBS Transit confirmed that every one of his answers was correct.

Most of the enthusiasts fell in love with buses in their childhood.

Combined, they are a walking encyclopaedia on Singapore buses.

They know the different models of buses that ply the various routes, the engine specifications of every bus, and even when a bus switches to a different route.

Never mind that some of them own cars and don't take buses.

"It makes it more convenient for us to chase buses," said Mr Poon Ngai Seng, 33, a teacher, who has no qualms driving from his Sengkang home to Tuas just to catch a glimpse and take a photo of a particular bus model.

Mr Lim aims to memorise the registration numbers and photograph every single bus in Singapore.

He said he has collected 24,000 photos of buses since he started in 2003.

JOYRIDES

He has also collected 10,000 old bus tickets, some given to him by friends and relatives, including 600 old blue Transitlink farecards.

Mr Jack Au Yong, 21, a national serviceman, has 16,000 photos. He loves collecting bus guides, and now has 600, dating back to 1999.

Bus fan James Lee, 46, a realtor, said he belongs to a group of about 20 who meet twice a month to chase buses, take joyrides together, and look out for buses to take photos.

On his own, he spends his spare time modifying bus models.

In his showcase, which he calls his miniature depot, Mr Lee has a fleet of 100 bus models, which he estimates cost him close to $6,000. He started his collection in 1997.

Said Mr Lee: "To me, a bus is not just a bus. Every bus is different, from the fabric of the seat, the aircon louvres, to its shape and design, its bodywork, chassis, wheel, engine and control mechanism."

He remodelled four toy buses into SBS Transit buses, even adding passengers and drivers in the buses.

Mr Poon has 20 old bus service plates. He made formal written requests to SBS Transit to let him have them.

He has been taking photos of bus ads too, since 1997.

He has 10,000 photos in his collection.

The bus fans say they face similar reactions from family and friends.

Said Mr Lee: "Our families and friends think we are weird. But for the married men among us, our wives agree that our chasing buses is better than chasing other women!"

Mr Poon also faced some complaints from his wife due to his obsession with taking photos of buses.

He said with a laugh: "When we were on holiday overseas, my wife complained that I took photos only of buses and not of her."

Now their love for buses has been put to good use with the publication of a book by a local bus company.

BOOK

Mr Lee, Mr Lim and Mr Poon were so enamoured of buses that they approached the local company. They wanted to research and write a book on the company's history in bus manufacturing.

With the help and sponsorship of Soon Chow Corporation, which manufactures and assembles buses, they produced 600 copies of a book, "80 years of bus and coach building. The Soon Chow Story".

They even contributed some photos from their private collection, in addition to old photos taken by the managing director, Mr David Soh, 50.

The bus fans took a year to conceptualise, research, write and edit the book.

"It's the fruit of our labour and symbol of our passion," said Mr Lim.

Mr Soh said: "I thought I was crazy about buses until I met them.

"They go around the island chasing buses just to take photos of them, which I don't," said Mr Soh.

But he refuses to brand them as weird.

Said Mr Soh: "Every collector can be fanatical about the things he collects, and it's no different with these bus fans. They are just living out their boyhood passion."