In a few years time, an electronic road pricing system will be introduced into traffic congested areas around the major cities in the Netherlands. The in-vehicle system component, the On-Board Unit (OBU), contains a chipcard needed for toll payment. An important OBU function is to present information to the driver concerning the transaction, the remaining credit and operational status of the OBU. However, this may result in adverse traffic safety effects because of driver overload or distraction. A literature review was conducted to derive recommendations for OBU design specifications that are aimed at minimizing possible adverse traffic safety effects. Because auditive signals are inherently attention attracting and often require the driver to look at a visual display for more information on the systems' initiative, the presentation of auditive signals is not recommended with a few exceptions. However, workload induced by auditive signals may be lower compared to visual messages. The visual workload induced by visual messages may result in negative safety effects. Mental and manual workload may also affect safety, but this is often caused by a need to look away from the external visual scene. Care must be taken to design the visual messages in such a way that the glance duration and glance frequency are as low as possible while the driver is free to choose when he wants to look at the display.
Abstract