What's BART?  San Fransiscans know it as "Bay Area Rapid Transit."  Simpsons fans know him as an 8-year old brat (a purposeful anagram?).

In bridge, it is a convention developed by Les Bart. It is used after the auction begins specifically:

 

West	North	East	South
1	Pass	1NT	Pass
2	Pass	??

Typically, to use this convention we assume 1NT was forcing (or maybe semi-forcing).

Responder can now bid a conventional 2 to show many possible hand-types (we will get to that in a moment).

So, in the auction above, if East bids anything other than 2, his bids are natural and would mean:
2: Natural, Weakish
2: Natural, Weakish (either a very weak 3-card raise, or more normally a 2-card preference and about 6-9 HCP).
2NT: Natural
3: Natural (but more of a courtesy raise. With a better hand, start with 2).

3: Natural -- to play (because there is no natural 2 bid available)
3: Natural -- stronger than 2
3=3-card limit raise
3NT= Natural

 

Aside from all those natural calls, responder has the "BART" 2 call available. To bid 2, he can have any of these hand-types ( 1-1NT-2-2 = )  :

1) A good raise to 3 (responder will bid 3 next)

2) A hand with exactly 5 and 2 (opener will bid 2 if he can stand to play in hearts opposite a 5-card suit)
3) A good preference to 2
4) A good hand with diamonds (responder will bid 3 next)
5) Some other "unsure" decent hand--just waiting to hear opener bid again

 

What does opener do after the artificial 2 bid?

First of all, he alerts it.
Then he can do any of the following (1-1NT-2-2- ) :

Pass: Not allowed

2: Willing to play in hearts if responder has 5 (usually a doubleton heart)
2: No tolerance for hearts (usually a singleton heart, could be 6 and 4).
2NT: Natural, extras
3: Natural 5-5 in blacks
3: Artificial, saying: "If you have hearts, I have a GREAT hand -- something like a 5=3=1=4 maximum"

3 and higher: Not a good idea

Warnings:
This is just a summary of the basics of BART.

There are several variations possible (One is called "Lisa" -- a Simpsons reference.)
As usual, make sure to discuss if on by a Passed Hand (I say YES), or if there was interference (I say NO).

 

 

The 2 bid after 2 is alertable. 1-1N-2-2-3 to show hearts is alertable.

 

_{Last updated: Nov, 2012}