Evaluating Driver Response to a Dynamic Speed Feedback Sign at a Freeway Exit Ramp Considering the Sign Design Characteristics and Lateral Installation Position

Research was conducted at a freeway exit ramp with significant horizontal curvature to evaluate the effectiveness of dynamic speed feedback signs (DSFS) as a speed reduction countermeasure. Several aspects of the DSFS were evaluated, including display size, border type, lateral installation position, and vehicle detection range. Three different full-matrix DSFS were utilized, which included: 15-inch display panel with yellow border, 18-inch display panel with yellow border, and 18-inch display panel with no border. Each sign was individually installed and tested at identical locations near the start of the exit ramp curve, in both the traditional right-side-mount and an alternative forward-mount within the exit gore area. Speed data and message activation location were collected for vehicles approaching and entering into the curve across the various sign test conditions. Overall, the presence of a DSFS positioned near the start of the curve resulted in curve entry speeds that were, on average, 3.5 mph lower than without a DSFS present at the site. The lowest curve entry speeds were observed for cases where the message activated when vehicles were within 250 to 400 ft of the curve. Interestingly, earlier message activation did not contribute to further speed reductions, although later activation substantially diminished the speed reduction effects. Regarding DSFS lateral position, both the side-mounted and forward-mounted DSFS installations resulted in similar curve entry speeds. Furthermore, there were no discernable differences in curve entry speeds between the 15-inch and 18-inch display panels, although the inclusion of a yellow sign border improved performance.

Safety Design Strategy for Highway Interchange Exit Ramp

Highway is an important type of road in China’s road network, and it also carries a larger portion of transportation task. Safety is the first indicator in the stage of its use, so it is necessary to carry out safety design focusing on the highway interchange exit ramp to effectively prevent traffic accidents. Therefore, in this paper, the important significance of the safety design of the highway interchange exit ramp and the key factors affecting its safety were discussed and studied in detail, and finally corresponding strategies were proposed for discussion and communication.

Study on the occlusion of the visibility window on highway exit ramps

Traffic accidents frequently occur at the nose of highway exit ramps for a variety of reasons. When attempting to take an exit, a driver’s line of sight may be obscured by the curvature or slope of the main expressway, roadside vegetation, traffic signs, and other vehicles traveling alongside. These increase the likelihood of accidents due to inaccurate or poor driver judgement when approaching a highway exit. Because of emotional responses that accompany the possibility of missing an exit, many drivers act irrationally through haphazard acceleration or braking, aggressive lane changes; in some cases, even coming to a complete stop and reversing against the flow of high speed traffic to correct their course. This study applies to curved highway exit corridors with a poor line of sight. The total visible area of the exit ramp is defined in accordance with the design specifications of both the highway routes and exit ramps, which was then further refined by considering the driving characteristics of both the drivers and of surrounding traffic. This study set out to establish a reliable occlusion model of highway exits with the following goals in mind. Geometric equations describing the area and volume of the target area of the exit ramp are established. Discrete expression equation was deployed to establish the occlusion model for the target area within the visual field. Parameters taken from specifications of the Hunan section of the Shanghai-Kunming Expressway are used for multiple calculations, in which obstruction patterns of objects with the same width, and objects with different width at different positions are analyzed. Based on the patterns observed from stimulated experiments mentioned above, multiple effective measures were proposed to prevent the obstruction of the highway exit ramp. In summary, this study provides theoretical support for prevention of obstruction as well as an anti-occlusion model for better identification of the highway exit ramps by intelligent vehicle systems.

Comparative Analysis of Freeway Exit Ramp Terminal Design Practices to Deter Wrong-Way Driving in Different States

Although wrong-way driving (WWD) crashes are rare compared with other crashes, the severe outcomes resulting from these crashes make them an important traffic safety issue, especially on freeways. The initial point of origin for the majority of WWD crashes is the exit ramp terminal. During 2009–2013, the exit ramp terminals of full diamond and partial cloverleaf interchanges in Alabama experienced considerably higher frequency of wrong-way entries compared with those in Illinois. In this study, a comparative analysis is conducted between these two states to compare the differences in exit ramp terminal design practices and determine the differences that might have caused the relatively higher frequency of wrong-way entries at the exit ramp terminals in Alabama. The comparative analysis revealed that there is relatively higher usage of certain geometric design features and traffic control devices in Illinois, which contributed to deterring WWD. The lessons learned from this study can potentially benefit the 4E community (i.e., enforcement, education, emergency response, and engineering) in further understanding the best practices on off-ramp terminal design and traffic control devices features that have the potential to reduce WWD crashes on freeways.

The Permitted Dimension of Guide Sign in Freeway Tunnel Restricted by the Geometric Space of the Tunnel Vault

Traffic guide signs should be settled in a freeway tunnel when there is a short distance between the interchange exit ramp and the tunnel exit in order to provide enough reaction time for drivers. However, there is not enough space for guide sign in a tunnel adopting the same design method as the guide sign along the general segment of the freeway. The maximum dimension of a guide sign in tunnel should be studied firstly. Based on the analysis of the characteristics of the inner outline design of the tunnel and its relationship with the guide sign dimension, the study was classified into different combination conditions: left superelevation and right superelevation under two-, three-, or four-lane freeway tunnels, respectively. The essential elements, the horizontal and vertical clearances, the radius of the tunnel vault circles, the angle of the superelevation, and the allowance vertical dimension for future sign installation were all taken into account to establish the dimension model of the guide sign in the tunnel. The maximum dimensions of the guide signs were proposed under different combination conditions. The results indicated that there is only one set of the width and the height to obtain the maximum area of the guide sign in the freeway tunnel. The height of the guide sign reduces with the increase of its widths, and the area of the guide sign increases and then reduces with the increase of its width under the same grade of superelevation. The changing trend and extent of the dimension of the guide sign under left superelevation condition were different from those under right superelevation.

Searching for the “exit ramp”: Bereaved caregivers (BCGs) describe discontinuation of transfusions at the end of life (EOL) for loved-ones (LOs) dying from acute myeloid leukemia (AML).

e24000 Background: Transfusions may delay hospice care. This study examined how transfusions and other factors influenced care transitions, including decisions related to hospice care, for patients with AML from diagnosis to death. Methods: Nineteen BCGs participated in semi-structured interviews about their experiences. Interviews were audio recorded, transcribed and qualitatively analyzed. Results: The research team identified three stages in BCG experience: 1. Acceptance and Hope: BCG initial response to an AML diagnosis was acceptance of chemotherapy and transfusions as necessary to extend life and potentially cure the AML. Benefits of treatment were emphasized over potential harms or details. 2. Reading the Signals: BCGs learned to interpret information from a variety of sources to appreciate whether their LO was heading in the right direction or not. The signals included discussions with or decisions of the oncologist, changes or no changes in lab results, changes in the LO’s physical condition, and changes in care location in the hospital (e.g., ward bed to ICU bed). Signals were either cautionary or hard stops. Cautionary were seen as conditional, e.g., if things did not improve then LO may be at EOL. Cautionary signals were described as vague and ambiguous. Hard stops were clearer and were typically a clinician decision or recommendation to discontinue treatment and/or transfusions because there was no longer a possibility of benefit. 3. Searching for the Exit-Ramp: Hard stops precipitated awareness that death was imminent and an often-rushed search for how to care for the LO at the EOL. In retrospect the transition made sense to the BCG but they often felt unprepared at the time of transition. Conclusions: The benefits and burdens of transfusions are important signals to BCG about the EOL. Early cautionary signals and discussion may prepare BCG for transitions. Continuation of transfusions in hospice may eliminate a chance for critical conversations.