March 15 (Reuters) - Uber Technologies Inc will cap surge pricing in the Washington area at 3.9 times base fares during the shutdown of the Metro system on Wednesday.

Lyft said it would offer new users $20 off their first ride during the shutdown.

The Metro system will undergo an unprecedented 29-hour shutdown for an emergency safety investigation of power cabling, officials said on Tuesday. (Editing by Stephen R. Trousdale; Editing by Sandra Maler)