Translink, which operates Northern Ireland buses, says two masked men dropped a bag containing the bomb on the woman's bus and ordered her to drive it to the police headquarters in Londonderry. IRA members have repeatedly targeted the fortified building.
The driver told the militants she would, but parked the bus at a stop and called police.
The episode illustrates the limits of today's small IRA splinter groups. The dominant faction, the Provisional IRA, killed nearly 1,800 people before calling a 1997 cease-fire and renouncing violence in 2005. Breakaway factions have killed a half-dozen people, but most of their attacks fail either because bombs are badly designed or police surveillance thwarts the attack.
The Provisional IRA pioneered the use of civilian drivers to deliver bombs in 1973, adopting the tactic to avoid the risk of their own members being arrested.
The Provisionals ruthlessly enforced the threats by taking the driver's family hostage and threatening to kill them if the driver stopped short of the target. Sometimes the Provisionals also followed the victimized driver in a second car and warned they would detonate the bomb, killing the driver, if they tried to raise an alarm. In 1990 the Provisionals killed one driver, a Catholic chef, as he arrived at his British Army workplace in Londonderry.
By contrast, recent IRA attempts to force civilians to deliver bombs all have failed, with the drivers stopping short of the target and raising an alarm.