from the end car. When the 1984/86 fleet of ICTS cars were introduced, floors were carpet-lined, intended as a way to showcase SkyTrain as an elegant world class system. However, as maintaining the carpets proved difficult and sanitation issues quickly became a concern, they were replaced with wax flooring in mid-1992. The Expo fleet of trains also initially equipped with passenger-initiated door buttons, meaning that individual door sets only opened at the push of a button when passengers wished to get on or off at a particular station. The buttons were removed between 1989 and 1991, due in large part to passenger confusion as to how to properly use the buttons as well as doors jamming, thus leading to the issue of frequent system-wide or area-specific delays. Between the late 1990s and early 2000s, just prior to the opening of the Millennium Line, SkyTrain gradually refurbished the entire Mark I train fleet in terms of design and layout. This included minor and major paint scheme changes before and following the shift from BC Transit to TransLink, upgrading of signage, changes to seating fabric colour scheme and seating arrangement, and a complete re-recording of the station announcement system that had been in use since 1985. From the beginning of the system's revenue opening in January 1986, SkyTrain operated daytime service with two-car and four-car Mark I trains running at a target five-minute frequency. During Expo 86, four-car trains were primarily used to manage the large-scale population flow of the fair. In the years following, two-car trains were operated on off-peak hours, late evenings and Sundays, while four-car trains were used to handle peak periods and large downtown events such as concerts, marathons, and hockey games. Two-car trains were gradually phased out between 1990 and 1993 in response to complaints about overcrowding. At the opening of the second part of the phase two extension to Scott Road station in 1990, six-car trains were used for the first time at reduced frequency while an operation glitch in the system's computer network had to be corrected and re-programmed. Prior to the opening of the Millennium Line, four-car trains became standard because SkyTrain could operate frequent service (about 150 seconds) during peak hours. The opening of GM Place (today called Rogers Arena) also brought an increase in the number of special events (hockey, concerts, and the short-lived trial of basketball) which required extended capacity during