English as it is Broken

The 'English as it is Broken' website is a good place to ask about grammar and other English language related questions. (http://www.stomp.com.sg/english/)
Here's one common problem....

Qn: I always have this problem with using "in", "at" and "on". It sounds silly that I can't even master these 3 simple words but please help: When do we use them in the following?
1) I am AT Suntec or I am IN suntec?
2) I am ON the train or I am IN the train?
3) There is a traffic accident ON the 3rd lane or IN the 3rd lane?

Ans: The table below will help you use the prepositions for locations:

At … a point
I am at home.
He is at the bus stop.
I am at Suntec City.
There is a traffic accident at the junction of Bendemeer and Balestier Road.

On … a surface
The boys are playing soccer on the field (not enclosed).
The cows are grazing on the open range (not enclosed).
I am *on the train to Bangkok.
There is a traffic accident on the road.

In … area/volume(within a space/place/enclosure)
I live in Singapore.
I am in a shop at Suntec city.
I went to Penang *in my car.
There is a traffic accident in the third lane (within the 3rd lane).
The cows are grazing in the pasture (enclosed).

Note that *on is generally associated with modes of public transport (bus, ship, plane) while *in is associated with private transport as in:
I went to school in my father’s car.
I am on the bus to school.
He travelled to KL on the train.

However, some speakers of English make a further distinction for public modes of transportation, using in when the carrier is stationary and on when it is in motion.
My friend stayed in/on the bus while I got off at Orchard Road.
The passengers sat in/on the plane awaiting takeoff.