The origin of the Modified Crash conventional method is unknown. This version of the Crash conventional method was employed and popular in England for many years before it became published in the United States. The version is employed in combination with the TWERB convention method, which is an acronym for Two-Way Exclusion Relay Bidding. The concept is devised to allow the intervenor to employ the bids of 1 and 1 overcalls with a strong, preemptive effect.

Note: Mr. Senior Brian has published this particular version of the Crash conventional method in his publication titled Conventions Today, which was published by Chess & Bridge October 2001. ISBN-10: 0953021815 / ISBN-13: 978-0953021819

Overcalls

Double:	Promises a Heart suit with good to semi-solid values.
1:	Promises a Spade suit with good to semi-solid values.
1:	Promises a two-suited holding of the same color: either Spades and Clubs or Hearts and Diamonds. The two suits are unspecified but must contain at least a 4-4 distribution with values located in the suits.
1:	Promises a two-suited holding of the same rank: either both Major suits or both Minor suits. The two suits are unspecified but must contain at least a 4-4 distribution with values located in the suits.
1NT:	Promises a two-suited holding of the same shape: either rounded, Hearts and Clubs, or pointed, Spades and Diamonds. The two suits are unspecified but must contain at least a 4-4 distribution with values located in the suits.
2:	This is a Twerb overcall showing either the suit above the suit bid, Diamonds, or a two-suited holding with at least a 5-5 distribution containing the suits below the bid suit, Spades and Hearts.
2:	This is a Twerb overcall showing either the suit above the suit bid, Hearts, or a two-suited holding with at least a 5-5 distribution containing the suits below the bid suit, Clubs and Spades.
2:	This is a Twerb overcall showing either the suit above the suit bid, Spades, or a two-suited holding with at least a 5-5 distribution containing the suits below the bid suit, Diamonds and Clubs.
2:	This is a Twerb overcall showing either the suit above the suit bid, Clubs, or a two-suited holding with at least a 5-5 distribution containing the suits below the bid suit, Hearts and Diamonds.
2NT:	Promises a two-suited holding of the same shape: either Rounded, Hearts and Clubs, or Pointed, Spades and Diamonds.

The suit overcalls on the two level are used to show two-suited holdings of the same color or rank.

Continuances

Any and all continuances depend entirely upon the overcalls of the intervenor and the responses of the advancer.

1.	The overcall is Double or 1: Any new suit by the advancer is natural. Any jump in a new suit shows an immediate fit. A first response of 1 No Trump is an invitational relay and game-oriented. After a 1 NT first response the intervenor is requested to bid a Puppet 2, after which the advancer is able to show his own suit.
2.	If the 1 No Trump overcall of the intervenor is doubled by opponent: Any redouble by the advancer is a relay to 2, which the intervenor must bid if the opener passes. In the case that the advancer passes the double by the partner of the opener, then the intervenor's bid of the lower-ranking of his two-suited holding (either Clubs if both Rounded suits or Diamonds if both Red suits) promises that the Minor suit is the better of the two-suited holding. If, however, the intervenor redoubles, then this shows that the Major suit is better. In the latter case of a redouble by the intervenor, the advancer bids an automatic 2, which allows the intervenor to pass with the Rounded two-suited holding or correct with the Pointed two-suited holding.
3.	After an Overcall by the Intervenor at the Two Level: The advancer will either pass or correct depending on which suit held is better suited. If the partner of the opener doubles, a pass by the advancer promises at least a 5-card good suit in the suit doubled. A redouble, after a double by the partner of the opener, is a transfer bid to the next higher suit, which allows the intervenor to then bid his own suit.
4.	When the defender in Second Position passes and the responder bids the negative 2, the bids of the intervenor in Fourth Position have the following meanings:
	Double: Promises a two-suited holding of the same color: either Spades and Clubs or Hearts and Diamonds. The two suits are unspecified but must contain at least a 4-4 distribution with values located in the suits.   1: This bid is natural.   1: This bid is natural.   1NT: Promises a two-suited holding of the same shape: either Rounded, Hearts and Clubs, or Pointed, Spades and Diamonds. The two suits are unspecified but must contain at least a 4-4 distribution with values located in the suits.   2: This is a Twerb overcall showing either the suit above the suit bid, Diamonds, or a two-suited holding with at least a 5-5 distribution containing the suits below the bid suit, Spades and Hearts.   2: This is a Twerb overcall showing either the suit above the suit bid, Hearts, or a two-suited holding with at least a 5-5 distribution containing the suits below the bid suit, Clubs and Spades.   2: This is a Twerb overcall showing either the suit above the suit bid, Spades, or a two-suited holding with at least a 5-5 distribution containing the suits below the bid suit, Diamonds and Clubs.   2: This is a Twerb overcall showing either the suit above the suit bid, Clubs, or a two-suited holding with at least a 5-5 distribution containing the suits below the bid suit, Hearts and Diamonds.   2NT: Promises a two-suited holding in both Minor suits.

With a strong partnership understanding and solid partnership agreement, the advancer can distinguish practically from the outset between weak and strong interventions in the Major suits and also between two-suiters with either a 4-4 or a 4-5 distribution and those holdings with at least a 5-5 or longer suit distributions.

If you wish to include this feature, or any other feature, of the game of bridge in your partnership agreement, then please make certain that the concept is understood by both partners. Be aware whether or not the feature is alertable or not and whether an announcement should or must be made. Check with the governing body and/or the bridge district and/or the bridge unit prior to the game to establish the guidelines applied. Please include the particular feature on your convention card in order that your opponents are also aware of this feature during the bidding process, since this information must be made known to them according to the Laws of Duplicate Contract Bridge. We do not always include the procedure regarding Alerts and/or Announcements, since these regulations are changed and revised during time by the governing body. It is our intention only to present the information as concisely and as accurately as possible.