EXAMINING THE EFFECTS OF A SIGNLESS ROADWAY: Virtual Traffic Control Devices and their Potential for Replacing Traditional Post-Mounted Traffic Control Devices

Abstract

EXECUTIVE SUMMARY In recent years, there has been an ever-increasing demand for the integration of technology into vehicles. This demand comes from the expanding use and dependency on smart phones, in-vehicle entertainment, computers and the Internet, and the desire to create a “smart car” to optimize the productive use of travel time. As this expansion in in-vehicle technology continues, obvious concerns exist with the number of potential driver distractors added. Technology-based distractors have the potential to attract drivers’ attention away from the driving environment and increase the probability of driver error. Nevertheless, technologies do provide the opportunity for integrating safety benefits, and it is necessary to consider how the availability of these technologies can enhance the safety of the driving task. Traffic control devices (TCDs) provide the primary form of communication with drivers as they navigate the transportation network. Many common roadway scenarios, confounded by traffic congestion and distractors, can cause drivers to miss important TCDs, specifically post-mounted signage, and the information they convey. However, advanced invehicle technologies may allow for a more focused presentation of TCD information such that communication is optimized for the scenario being presented. In a recent study by the Federal Highway Administration (FHWA), elongated pavement markings (EPM) were considered as a supplement to enhance post-mounted regulatory and warning signage. EPM signs were placed in the center of the travel lane directly in front of the driver creating a ‘head up’ reinforcement of the critical TCD information. The results of this research showed that regulatory and warning sign information placed directly in front of the driver to enhance the traditional signing methods increased awareness and decreased operating speeds improving compliance and safety behavior. Results further demonstrated that providing regulatory and warning sign information in a ‘head up’ presentation may be effective in reinforcing regulatory and warning messages to drivers and improving safety. Therefore, there is a need to determine if using in-vehicle technology to optimize the presentation of TCDs to drivers in the form of a head-up display (HUD) may lead to more effective driver communication demonstrated through TCD compliance and safer operating behavior. Furthermore, if HUDs are indeed the optimal way of presenting TCD information to drivers, a question can be explored pertaining to the future need of post mounted signs and other roadside placed TCDs. Many studies have found in-vehicle displays using HUD to be an effective form of communicating information to drivers (7, 30, 31, 33, 35). These devices work well with various navigation and lane departure information, however, they have yet to explore the broad array of TCDs and their applications in regulating and warning drivers as they traverse the transportation network. Given these findings, the next step was taken in this research to examine the application of such in-vehicle technology by using a HUD in conjunction with TCDs to convey critical regulatory and warning information to drivers.

The objective of this research was to use HUD technology to explore presenting TCDs in the drivers’ line of sight in order to determine if this technology and type of presentation could be used as a replacement for traditional post-mounted TCDs. Twenty test subjects were recruited, ranging in age from 20-68 years old, to participate in a research experiment to evaluate a selected set of regulatory and warning sign applications. Subjects were asked to drive through three different scenarios in the full-scale driving simulator at the UW-Madison Traffic Operations and Safety Laboratory. Scenario A was a completely signless roadway environment, producing unrestricted free-flow driving and natural driving behavior without TCD communication. Scenario B was a traditionally signed roadway following the Manual on Uniform Traffic Control (MUTCD) guidance adding the appropriate sign elements of traffic control to the drive. Scenario C was a virtually signed roadway, using the capabilities of the driving simulator, in which virtual traffic control devices were displayed in the same manner that they would be in an external HUD device. No post-mounted signs were included in scenario C. Average speeds were compared between critical points in eight curve segments (sign location, point of curvature, midpoint of the curve, and point of tangency) in an attempt to reveal the effectiveness of these virtual in-vehicle displays and their potential for replacing the traditional post-mounted roadside sign. While operating speeds were higher, on average, with virtual signage compared to post-mounted signage, statistically significant differences in speed were sparsely present. The results show that head-up displays could, in fact, be a viable option to safely and optimally replace traditional post-mounted TCD signage.