For the most part, strikes are scheduled well in advance. If you watch the headlines in the newspapers, watch or listen to news over the airwaves, or even just pick up those freebie newspapers they give away on the metro, you will see coverage.
Most of the time, strikes are called for one day only. There are circumstances, however, when the unions involved will invoke their right to renew the strike each day as they see fit. What typically happens is that the effect of the strike is worst the first day and then things get progressively better as the days wear on. But they can wear on. A transport strike in 2007 lasted three weeks; a SNCF strike in the south of France in spring 2010 lasted several weeks as well.
Transport strikes typically begin at 8 p.m. the evening before the called strike and continue through 8 p.m. the following day. In general, the subway tends to be more affected than buses, and the RER A and B more than other lines of the subway and suburban trains. Expect longer waits between trains, crowds on platforms, and crowded cars. The RATP posts information on the number of trains and buses expected to run on its Web site. For the RER C, D, and E, and suburban trains operated by the SNCF, consult the Web site www.abcdtrains.com. (Note: This site is only operational when disruptions in service occur, whether due to strikes, technical problems. or weather.) For information on intercity travel, you have to check the main SNCF Web site. For airlines, check with your carrier.
When a national strike is called, you can expect disruptions in the mail, street cleaning, trash pick-up, and government offices. Schools and hospitals may also be affected as well as state run television and radio stations.
Laws passed in 2008 affirm the right of workers to strike but also require that sufficient workers be available to provide a minimum level of service, particularly for public transport and schools. For transport, this means that a certain number of trains and buses must continue to operate. For schools, it means that personnel must be on hand to supervise children although not necessarily to teach. The definition of minimum service is not well specified in law, however. The bottom line is that workers retain the right to strike and while life can get quite inconvenient (for commuters, for parents, for businesses, and for people trying to do business with public agencies), nothing ever comes to a complete and utter standstill.