The Minnesota Department of Transportation (MnDOT) conducted a demonstration project as part of the Connected Vehicles Program to design, build, and test three new software applications to run on a commercially available personal navigation device (PND). The three applications that run on the PND (e.g., TomTom or phone running Android) use global positioning satellite (GPS) technology to: • Calculate and present mileage based user fees (MBUF) for the road on which a driver is traveling and an accumulated bill • Present in-vehicle signing (IVS) to drivers about specific zones they encounter (e.g., construction) • Present traveler information using probe vehicle data which will allow information to pass between vehicles and the infrastructure and allow drivers to see travel time information The overall goals of the larger project, entitled Minnesota Road Fee Test, were to: • Develop and validate the functionality of each vehicle acting as a probe and providing information to a central location • Provide route-specific traveler information to vehicles • Demonstrate the technical feasibility of a MBUF component, • Identify drivers’ opinions about the MBUF component and to identify the reaction to this component by the general public • Demonstrate the feasibility of delivering time-specific safety and warning messages on an in-vehicle display The goal of the study described in this report was to examine the IVS function for four zones and determine the utility and potential distraction associated with the IVS information. The specific zones of interest that were signed on the PND in this study were areas where speed zone changes occurred along the same roadway, notification of school zones, notification of construction zones, and notification of curves to assist drivers with preparing for transitions to new driving situations. Driving performance measures known to be related to distraction as well as subjective usability and workload measures were used to help identify potential distraction associated with the IVS information. Moreover, risk analysis was conducted to evaluate the safety associated with IVS technology, relative to status-quo safety levels. Forty participants (balanced for gender and across age groups) completed the study and were divided into two IVS conditions. The first IVS condition included the IVS information in addition to external (roadside) sign information (IVS +ES). The second IVS condition included only the IVS information, in the absence of external signs (IVS -ES). All information was displayed using an Android phone mounted on the center console of the vehicle within the driver’s view (i.e., in the same location where a manufacturer-installed navigation screen and controls would be located). A simulated driving route was developed in the HumanFIRST simulator using a real roadway network from southern Minnesota. Drivers in each condition drove the 24-mile-long simulated route that included freeway driving, two-lane rural road driving, and town driving with and without the PND system information activated. Baseline data was collected regarding all participants’ driving behavior when they drove the typical route with signage presented roadside and no IVS information displayed. Driving performance measures related to distraction (i.e., speed and lateral control) were collected during the drive. Participants also completed a series of usability questionnaires, as well as subjective measures of mental workload, for each of the driving conditions. The objective measures collected in this study (i.e., both driving performance and risk analysis) indicated that IVS technology would impact driving performance in the following manner: • When IVS is deployed in the absence of external sign information (IVS -ES), speeding behavior significantly increased relative to baseline levels. IVS technology was not observed to impact speeding behavior when external signs were also present (IVS +ES), however. • Risk analysis suggested that IVS technology (when used in conjunction with external signs) can improve the safety associated with frontal-impact crashes; however, the risk analysis demonstrated that safety across all crash types was significantly reduced below baseline levels in the IVS -ES condition. • Variability in speed reduced below baseline levels only when IVS information was presented in the absence of external signs (IVS -ES). Taken together with the speed data, it suggests that drivers in the IVS -ES conditions failed to appropriately adjust their speeds to the stated limit as frequently as did drivers in the other signage conditions. • Finally, deviations in horizontal lane position were not affected by either IVS +ES or IVS -ES conditions, relative to baseline performance. This suggests that driver distraction and lateral vehicle handling was not affected by the presence of the IVS technology. The subjective usability results provided additional information that clarified the driving performance findings: • Total mental workload, as measured by NASA-RTLX, was found to be greater during IVS use in the absence of external signs (IVS -ES). Workload levels were similar, however, between baseline conditions (i.e., external signs and no IVS) and when IVS was used in conjunction with external signs (IVS +ES). • Usability inventories found that subjective perceptions of the system’s usefulness significantly decreased after system use for both IVS conditions (i.e. IVS +ES and IVS -ES). Satisfaction ratings were consistent between pre- and post-system use for the IVS +ES group, but significantly decreased for the IVS -ES condition. Usefulness and satisfaction were both still overall rated positively after use in the IVS +ES condition; however, satisfaction became negatively rated when IVS information was provided in the absence of external signs (IVS -ES). Overall, the project was able to identify some of the preliminary driver effects that may occur when using a commercially available device with IVS information included. Some recommendations can be drawn from the results of this evaluation: • It was discovered that using the IVS system in the absence of external signs (IVS -ES) resulted in increased speeding behavior due to participants failing to adjust their speeds according to the posted levels. This increased speed resulted in significantly decreased levels of safety associated with various crash types. Moreover, subjective measures demonstrated both increased workload and decreased satisfaction associated with the IVS system in the absence of external signs. Although using IVS information in the absence of external signs would presumably save money on infrastructure costs, it is recommended that the current IVS system not be utilized in substitution of external signs. • Notably, analysis of driving performance metrics demonstrated that using the IVS system in conjunction with external signs (IVS +ES) resulted in driving behavior that is comparable to baseline levels (i.e., external signs with no IVS present). In fact, risk analysis discovered that the reduction in speeding behavior associated with the IVS +ES condition resulted in improved safety outcomes in the event of a frontal-impact crash. Moreover, subjective measures showed that overall usefulness and satisfaction ratings were still positive after IVS system use (i.e., with external signs present) and the total mental workload was similar to baseline rates. Therefore, it is recommended that the potential of using IVS information in conjunction with external signs be further explored. (Author/publisher)
Abstract