Browsing by Subject "Traffic signs"
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Item Evaluation of R1-6 Gateway Treatment Alternatives for Pedestrian Crossings: Follow Up Report(Center for Transportation Studies, University of Minnesota, 2017-06) Van Houten, Ron; Hochmuth, JonathanMonthly follow-up data confirmed that permanent in roadway installations of the R1-6 gateway treatment led to an increase in the percentage of drivers yielding to pedestrians at midblock and multilane urban and suburban locations from 15% to 70% and that these increases endured without any decrement over the spring, summer and fall of 2016. Speed data collected at each site showed 4 to 5 mph reduction in mean when motorists traversed the crosswalk when pedestrians were absent. These speed changes persisted over time. An additional study showed that placing the signs between 5, 10, 20, 30, and 50 ft in advance of the crosswalk were equally effective and they enticed drivers to yield further ahead of the crosswalk. Data on sign survival showed that signs mounted on a curb type mount with a flexible rubber attachment all survived while only 58% of the flush mounted signs with a pivoting base survived. Data showed that none of the signs mounted on top of the edge of a curb on a refuge island or median island, curb extension, or the curb on the edge of the roadway under FHWA permission to experiment were destroyed or damaged.Item Understanding and Mitigating the Dynamic Behavior of RICWS and DMS Under Wind Loading(Minnesota Department of Transportation, 2020-06) Linderman, Lauren; Guala, Michele; French, Catherine; Schillinger, Dominik; Finley, Nicole; Heisel, Michael; Nguyen, Lam; Stoter, Stein; Vievering, Josh; Zhu, QimingDynamic Messaging Signs (DMS) and Rural Intersection Conflict Warning Signs (RICWS) are roadside signs that feature much larger and heavier signs than are typically placed on their respective support systems. The excess weight and size of these signs, in conjunction with their breakaway support systems, introduces vibration problems not seen in the past. The AASHTO 2015 LRFD Specification for Structural Supports for Highway Signs, Luminaires, and Traffic Signals (SLTS) does not yet address vibration design for these nontraditional roadside signs. DMS and RICWS were instrumented in the field and numerically modeled to explore their wind-induced behavior. A dynamic numerical model was validated with experimental field data and used to evaluate the fatigue life of the DMS support system instrumented in the field. The resulting fatigue life differed significantly from the equivalent static pressure analysis prescribed in the AASHTO specification. The fatigue life of the DMS instrumented in the field was conservatively estimated to be 23.8 years. Based on data collected from a RICWS instrumented in the field and experiments done on a scaled model of the RICWS at the St. Anthony Falls Laboratory, vortex shedding was identified as the predominant wind phenomena acting on the RICWS structure. Three modifications were proposed to reduce the impacts of vortex shedding. The investigation of these newer sign types highlights the importance of considering the impact of dynamic behavior and vortex shedding on the structural design.Item Vehicle Automation and Transportability of Crash Modification Factors(Center for Transportation Studies, University of Minnesota, 2019-07) Davis, Gary A; Gao, JingruAlthough the Highway Safety Manual (HSM) now provides empirical tools for predicting the safety consequences of highway engineering decisions, these tools represent the prevailing driver and vehicle conditions in the United States during the last few decades. As automated vehicles improve in capability and increase in market share, these conditions will change, possibly affecting the accuracy of HSM predictions. This report investigates the feasibility of using “transportability” analyses, developed by Judea Pearl and Elias Bareinboim, to assess the “transferability” of crash modification factors (CMF) to new situations. An overview in Chapter 2 concludes that transportability analysis is, in principle, possible provided one can describe a causal mechanism that explains how a CMF works. Chapter 3 then describes developing such an explanation for pedestrian hybrid beacons (PHB). In Chapter 4 the explanatory model developed in Chapter 3 is used to assess the transportability of existing estimates of PHB CMFs to a hypothetical situation where vehicles with autonomous braking are present.