We refer to the letter, It is an offence to park on double yellow line" published in Lianhe Zaobao on 28 December 2017.
Officers from the Police Security Command, as well as other Police Officers will seek to observe traffic rules and regulations. However, there will be occasions when they may have to exercise their discretion, and make exceptions.
For example, the official vehicles may need to be in close proximity to the event location for security reasons and to facilitate quick evacuation. When responding to law enforcement situations, Police vehicles often have to be parked in locations which enable swift, effective operations. And often, if there is no easily accessible car park, (which fit the right security profile) then, so as not to expose the person under protection, the vehicles will be driven near to the place where it is suitable to arrange a pick up, even if otherwise parking in such a place is not allowed. Police officers will assess the situation, including public safety, when making these decisions. They are trained to do so.
This is similar to what is being practised by Police forces in many other countries.
Source: Singapore Police Force