Others argued that the word was not part of a greater metaphor, but of an old English insult whose meaning has shrunk over time. This law requires, inter alia, certain categories of public transport workers (e.g. B.-train and bus driver) to notify their employer 48 hours in advance if they want to strike. If they strike without first declaring their intention, they are punished. Unionized workers are sometimes forced to cross strike lines set by other unions, as their organizations have signed non-strike clause contracts. The non-strike clause generally provides that union members do not take strike action during the term of the contract; Such actions are called sympathy or secondary strikes.