Jonathan Upchurch

Simulation assessment of incident detection by cellular phone call-in programs

This research study was designed to assess by simulation the efficacy of incident detection by cellular phone call-in programs. The assessment was conducted by varying the proportion of drivers with cellular phones on the highway so as to mirror the cellular industry statistics that show a continued growth of ownership of cellular phones in the United States. An analytical model, which combined simulation and the limited field data available in the literature, was used to determine measures of effectiveness of the cellular phone-based detection system.The results showed that a cellular phone detection system offers fast incident detection times and higher detection rates for both shoulder and lane blocking incidents. For example, in moderate traffic flow (i.e. 1,550 vehicles per hour per lane), 90 percent of incidents blocking two lanes were detected in 1.5 minutes when the proportion of drivers with cellular phones was one out of 10 drivers, even with only 20 percent of them willing to report incidents. When the current proportion of cellular ownership, i.e. 1 out of 3, was used in the simulation, the detection time improved to 0.8 minutes.The simulation analysis of incident detection by cellular phones also showed that there is a direct relationship between the probability of detection and the detection time; that is, the specification of a higher detection rate resulted in slower detection times. This is in sharp contrast with the results of field study of automatic incident detection (AID) systems which demonstrated an inverse relationship between probability of detection and detection time.

Guide signing for two-lane exits with an option lane: Evaluation of human factors

In recent years U.S. freeways have seen an increase in the number of exit ramps that feature a two-lane exit with an option lane. This is a situation in which motorists in the rightmost lane of the freeway must exit, and those in the adjacent lane may either exit or continue on the mainline. Communicating information to the motorist about this type of exit is exceptionally difficult. Ideally, a sign should convey the following: (a) If you stay in the right lane, you will be forced to exit. (b) If you wish to exit, you may do so from either the right lane or the adjacent lane. (c) If you are in the adjacent lane and wish to continue on the mainline, you need not change lanes. Making all of these discrete concepts obvious in a simple sign is challenging, and there is no standard sign design for this situation in FHWAs Manual on Uniform Traffic Control Devices for Streets and Highways (MUTCD). As a result, at least eight different sign designs are being used throughout the United States. This paper presents the results of an NCHRP human factors study conducted to identify the best design for a guide sign for this type of exit. Four candidate sign designs were evaluated with 96 test subjects in a driving simulator. Measures of effectiveness included the number of missed exits and the number of unnecessary lane changes. On the basis of the study results, one of the four designs is recommended for inclusion in the MUTCD.

FREEWAY GUIDE SIGN DESIGN WITH DRIVING SIMULATOR FOR CENTRAL ARTERY-TUNNEL: BOSTON, MASSACHUSETTS

The Central Artery–Tunnel (Interstate 93) through downtown Boston, Massachusetts, is being reconstructed as a tunnel 2.4 km (1.5 mi) long. Within the tunnel several exits require guide signing for motorist safety and efficient traffic operation. Design and placement of this signing bring challenges due to the tunnel’s low ceiling height of 5.19 m (17 ft) and horizontal and vertical curvature that reduces the distance from which motorists can see the signs. Tunnel guide signs may also be blocked from view by large trucks, due to the lower than usual mounting height. Reconstruction of the Central Artery will improve traffic operations by reducing the number of exits and entrances on Interstate 93 from the current 27 exits and entrances (two-directional total) over 3 mi to 14. Yet, the tunnel will have 7 exits, 3 of them compressed into a southbound tunnel segment 1250 m (4,100 ft) long. These conditions may cause drivers—especially unfamiliar drivers—to have difficulty obtaining guidance information for their exit. This can lead to driver frustration and a reduction in safety caused by abrupt lane changing and other maneuvers. To address these problems with improved sign design and placement, a study using a driving simulator was undertaken. A computer-generated roadway through the tunnel was developed to replicate the tunnel geometry (including horizontal and vertical curvature and ceiling height) and sign placement. Test subjects drove through the simulated tunnel to evaluate the developed signing alternatives. The driving simulator was also assessed as a tool for improving freeway guide signing.

MODELING DETECTION OF INCIDENTS BY DRIVERS

Abstract An analytical model was developed to assess the detection of freeway incidents by drivers using advanced communications technologies. Drivers can report incidents to a highway agency by voice or by digital messaging either directly or through roadside beacons using a fixed or portable wireless communications system such as a cellular telephone. A FRESIM model was used to simulate shoulder and lane-blocking incidents occurring under variable traffic flow rates. The proportion of drivers with an in-vehicle communication medium arriving upstream of an incident and the degree of the drivers’ reporting propensity were introduced as controlled variables. A discrete probability model was used to represent binary reporting decisions of drivers arriving upstream of an incident. The results showed that all incident types that were simulated could be detected in a short time with high probability of detection. The data indicated that all incident types, regardless of the prevailing traffic volume at the time of their occurrence, were detectable in less than one minute if one of five drivers on a freeway had an in-vehicle communication medium and was willing to use it to report the incident. Of special importance is that at the end of 1995 there was one cellular telephone user per five licensed drivers in the United States. The results of the modeling further showed that other factors affecting the detection performance of a driver-initiated incident detection process were the willingness of drivers to report incidents, the length of roadway within which an incident is visible to a driver, and the austerity of the highway agency’s procedure for mitigating false reporting.

MONITORING URBAN FREEWAY INCIDENTS BY WIRELESS COMMUNICATIONS

The efficacy of the driver-initiated incident detection system was assessed by modeling the use of new communications technologies to mitigate problems that beset current cellular call-in programs, problems such as insufficient information on incident location, false reporting, and duplicate calls. An analytical model supported by field data for several important variables was used to determine the system performance measures, that is, the detection rate, mean time to detect, and false alarm rate. The results indicate that with the implementation of new technologies that lead to the automatic geolocation of the driver initiating an incident call, the driver-initiated detection system is effective. The system achieved good detection rates and faster detection times across all simulated incidents occurring under variable traffic flow rates that ranged from light traffic to congested traffic. For instance, even when the proportion of drivers with cellular phones was 1 out of 10, with only 10 percent of them willing to use their phones to report the incidents, close to 80 percent of the incidents were detected within 2 min. This result is consistent with the results of the field studies and shows that even better detection performance can be achieved if current levels of cellular phone ownership in the United States are considered and if drivers’ reporting propensity is raised. It is noteworthy that the Cellular Telecommunications Industry Association reported that there was one cellular phone user per two licensed drivers in the United States at the end of 1999.

A Human Factors Evaluation Of Alternative Variable Message Sign Technologies

This paper presents the results of a study evaluating three different Variable Message Sign (VMS) technologies: shuttered fiberoptic, light emitting diode (LED), and electro-magnetic flip disk. The technologies were evaluated for target value, legibility distance, and viewing comfort.

A Human Factors Evaluation of Freeway Guide Sign Lighting Systems

The objective of the study was to identify a lighting system for freeway guide signs which is more economical and which adequately satisfies motorists needs in terms of legibility, illumination, color rendition, and other factors. Through the use of technical data and specification review, photometric tests, and computer analyses, ten lighting systems were selected for field testing (10–14 months). Luminance levels, power consumption, maintenance requirements, and lamp life were noted. A human factors study determined legibility distance and rated viewing comfort, lighting uniformity, and color rendition. Senior citizens and young adults were used to detect possible age-related differences. None were noted other than seniors placed more importance on color rendition. It was determined that the differences between the best human factors performing lighting systems and the best regarding economics was only marginal concerning human factors. The most economical system was thus recommended.

Zion National Park, Utah: Enhancing Visitor Experience Through Improved Transportation

In 2000, Zion National Park in Utah introduced the Zion Canyon shuttle to transport visitors into Zion Canyon while alleviating traffic congestion and improving visitor experience. Now in its 16th season of operation, the shuttle is successfully accomplishing those goals and receives kudos from park visitors. The continued and increasing popularity of Zion National Park, with 3.2 million visitors in 2014, has created new transportation challenges at the gateway to the park. At the gateway area, visitors arrive at the park, usually in private automobile, and change modes to ride the shuttle into Zion Canyon. The challenges include waiting times of 10 to 22 min at the parks primary entrance station on many summer days, parking lots at the park visitor center that are routinely filled to capacity between 11:30 a.m. and 2:30 p.m. on most summer days (forcing visitors to park on the streets of Springdale, Utah, the parks gateway community), insufficient parking for recreational vehicles, visitor crowding, and a variety of related issues. This paper offers analyses of the primary transportation issues and describes alternatives for improving transportation and visitor experience. The needed entrance station capacity to avoid queuing and waiting times is presented, along with alternatives for providing that level of capacity. An evaluation of parking demand and parking alternatives being considered by the park is described. An analysis of shuttle bus capacity shows an ability to absorb additional hourly demand created by entrance station improvements.

Preserving a Historic National Park Roadway: The Hermit Road

The Hermit Road is a historic roadway in Grand Canyon National Park, Arizona. It was first constructed in 1912 by the Santa Fe Railroad and improved from 1934 to 1935 by the Bureau of Public Roads and the National Park Service. An 8-mi scenic roadway along the south rim of the Grand Canyon, the Hermit Road offers several overlooks and parking areas that give the visitor breathtaking views of one of the seven natural wonders of the world. The original design of this roadway reflects many features of context-sensitive design. Historic features of the roadway include stone masonry walls at overlooks and pullouts, weep holes in masonry walls, and stone culvert headwalls. After seven decades, the Hermit Road was showing its age. The National Park Service faced the challenge of how to retain a high level of historic integrity while also rehabilitating and improving the Hermit Road. The pavement surface was in poor repair; some of the road and overlook historic features were endangered. The narrow road, 18 to 20 ft wide, presented a safety concern. Improvements constructed in 2008 included widening and resurfacing; the enhancement of existing overlooks, parking areas, and trails; and the addition of a pedestrian and bicycle trail on a separate alignment. These improvements were accomplished with minimal impact on historic and natural resources. This paper describes the environmental compliance process, roadway design issues, and how historic integrity was generally retained in the roadway design. The perspectives of historic preservation, environmental protection, resource conservation, and roadway design are presented.

Signing Two-Lane Freeway Exits with an Option Through Lane in Extreme Conditions: Anatomy of Drivers' Behavior

Two-lane freeway exits in which the left-hand exit lane also continues as a through (option) lane are becoming increasingly common. Potential problems can arise at these exits when drivers become confused by the signing and can lead to increases in driver frustration, incidents, and congestion. These problems have not been studied in any detail, especially in circumstances in which the signs recommended in the Manual on Uniform Traffic Control Devices for Streets and Highways cannot be used. Such is the case in the underground sections of I-93 through downtown Boston, Massachusetts, where the signs can be no more than 3 ft high. To arrive at a better understanding of these problems, the Massachusetts Highway Department evaluated a number of different ways of informing drivers that the left-hand lane of a two-lane exit functioned as both an exit lane and a through lane. The entire underground sections of northbound and southbound I-93 were simulated on a computer. Participants in an experiment sat in an actual car surrounded by three screens onto which was projected the virtual world and manipulated the controls of the car just as they would those of an ordinary vehicle. The participants were given a particular destination on each drive. The exact path was recorded, and misses and unnecessary lane changes could be derived from the recording. Six different signs were evaluated in three experiments. A function that could be used to rank the effectiveness of a given sign on the basis of the participants’ different responses to the sign was developed. Clear recommendations for the signing of two-lane freeway exits with an option through lane in extreme conditions emerged from the experiments.