Have any buses been stopped by traffic police for speeding? No. In fact it is impossible for most buses to speed here in Singapore as most are fitted with a 60kmph speed limiter. Now you know why buses are slow even on expressways. Other than DDs & Bendies which have been exempted due to the fear that they may not be able to climb slopes easily (that's wat i heard?), there are a few buses that are not fitted with the speed limiter, and these buses are usually specially deployed on long-distance express svcs (predominantly 858 ) to give it an extra edge over other svcs. whether tis is illegal or not i dunno, but i have sat on one 858 that goes at 120kmph for last bus, and surely there will be others here that would testify that with their own neck-breaking rides on some 858 buses. once in a lifetime experience.

In the olden days, it is possible they may get caught by the speed cameras (especially Yishun Ave 2 & Holland Rd ones) but now they can't even get caught if the drivers step hard on their pedals.
How to know if a bus is fitted with a speed limiter: look out for the Mannesmann Siemens VDO label near the front door/window together with the road tax labels there.
Can I take pictures at the busbay of 170/causewaylink at woodlands checkpoint?Are there any sercurity issues?You can do so, provided you do it fast and act natural, like out of interest. Just don't get spotted by the staff, policemen and possibly, the SBST traffic inspectors.

Why are there no new services by CSS
PTC wants to phase out CSS and thus no new services will be introduced or amendments made to extend its current reach. In fact, the CSS services are slowly disappearing year by year. 603 was the last bus to go. However, they are allowed to keep running the current routes, possibly cos they are still in (some) demand and they don't wan to do "rationalisation " just for the withdrawl of CSS services.

a short bit on the history of CSS/Tibs
Since the 1970s, CSS minibuses were running around providing shuttle services between various estates & the CBD. In 1982 (or around there), the government wanted a new competitor in the local bus services industry to provide some competition and CSS was chosen to break SBS's monopoly. In 1983, Tibs inaugrated with 2 services (164 & 167 i think), and both CSS & Tibs became subsidiaries under Tibs Holdings.