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The Netherlands schedules track maintenance to improve track workers' safety.

Article Excerpt
After several fatal accidents, improving the safety of rail-track workers became a political priority in The Netherlands. Maintaining the track was one of the most dangerous jobs in the country. ProRail divides its infrastructure into working zones to be taken out of service during maintenance. We developed a two-step method of constructing a four-week maintenance schedule in which each working zone of the main lines is closed to trains at night exactly once. The alterations in trains' departure and arrival times are within the restrictions imposed by train operators. Workers have accepted the resulting schedule, which provides them with a manageable maximum workload per night. Such a schedule is unique in Europe. It has been in operation since 2000 and has clearly proven its benefits.

Key words: facilities-equipment planning: maintenance, replacement; government: services. History: This paper was refereed.

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After railroad track workers suffered several fatal accidents, the Dutch government decided to protect track workers in space and time while they were working on the tracks. It summarized this decision in the statement "werkploeg is trein," or a work crew is equivalent to a train (in the sense that both require the same precautions to avoid collisions). This means that if track workers are working in part of the corridor, that part should be closed to all traffic. ProRail therefore divided its infrastructure into basic working zones and asked us to develop an efficient maintenance schedule based on these working zones. The government delegated the management of the railways to ProRail (http://www.prorail.nl), which is responsible for the capacity, reliability, and safety of rail infrastructure. We used operations research (OR) techniques to construct a four-week, cyclic, preventive maintenance schedule. Such a schedule is unique in Europe. ProRail has used it since 2000, and it has clearly proven its benefits.

OR models and techniques have played an important role in railway applications. Some OR models support decision making with respect to railway infrastructure (Harris and Ramsey 1994, Carey 1994, Hensher 1997, Higgins and Ferreira 1997, Higgins 1998, Hooghiemstra et al. 1999, Odijk 1999, Cheung et al. 1999). Higgins (1998) developed an optimization model for determining the allocation of railway maintenance activities and crews that best minimizes the disruption to and from scheduled trains. It minimizes the time a given track segment's service level is below a specified benchmark (by scheduling activities as early as possible). The method uses tabu search to find a solution to the problem. Cheung et al. (1999) developed a method of scheduling enough preventive maintenance work to avoid disrupting railway operations during the operational period (of about 19 hours every day). It schedules the maintenance work during the remaining time, which is less than five hours a day. Moreover, it follows a set of rules and procedures in scheduling the maintenance work (for example, safety rules). Higgins (1998) assumed that work crews can carry out maintenance activities during train service, which is not the case when "werkploeg is trein" is applied. Cheung et al. (1999) assumed that each day several hours were available for maintenance during which there were no trains, which is certainly not the case in The Netherlands.

The Safe Maintenance Project

In 2000, the Dutch railway network consisted of about 6,500 railway kilometers, more than 3,000 switches, and 400 yards. It handled about 5,000 trains per day. In 2000, it transported over a million passengers and 60,000 tons of freight per day. The network is operated mainly by the Dutch railways (http://www. ns.nl) and is fully financed and owned by the Dutch government.

In 1995 in Mook, a train hit and killed three track workers carrying out maintenance activities. This accident caused a national investigation, which showed that track workers had one of the most dangerous jobs in The Netherlands. Their individual risk (IR) was 3.4 deaths per 10,000 track workers per annum, three times higher than the IR in the building industry. The investigators concluded that to ensure safety, the railways should allow no trains on the parts of the rail infrastructure under maintenance. The track workers should be protected in space and time.

ProRail decided to combine...