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3.0 Signing, Markings and Channelization

3.6 Changeable Message Signing

Changeable message signs (CMS) at conventional plazas are primarily used for providing lane collection mode information, allowing the agency the ability to change a particular lane, such as from attended to unattended in either a combined ETC and ACM mode, or just one of these two collection modes. Conversely, an ACM collection mode can be converted to an ETC dedicated lane during times of high ETC demand. Flexibility in changing the collection mode of the lane allows better management of vehicle throughput and operational costs, although based on the survey data about half of the agencies, are not taking advantage of this flexibility. This lane type flexibility presumes the lanes are properly equipped and the physical features of the lane are conducive to safe travel in any of the selected collection modes. Facilities that charge or are contemplating charging time of day pricing typically use variable display modules combined with fixed static sign panels to show the current toll for passenger cars and possibly other vehicle classifications. Notwithstanding the above, CMS should only be deployed when multiple sign messages are required because of the significantly higher capital and operating costs incurred relative to a fixed static sign.

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