Impact of Arterial Characteristics on the Operational Performance of Traffic on Urban Arterials Near Diamond Interchanges

Urban arterials near freeway interchanges are vital segments of road infrastructure. While freeways have high mobility and low access, urban arterials have medium mobility and medium access. Designing facilities that can efficiently connect these two types of roads is complex. There is an increasing need in the profession to have an in-depth understanding of the operational performance of urban arterials, while no clear and straightforward recommendations exist to enumerate the impact of various design and operational elements on the operational performance of traffic on urban arterials. This dissertation suggests a step-by-step methodology to (a) comprehensively study traffic flow on urban arterials located in the vicinity of diamond interchanges, (b) quantify the impact of the urban street characteristics on lane changing, and subsequently, (c) study how lane change behavior impacts travel time. This research studied two dependent variables, and, as a result, two final statistical models were built to demonstrate the relationship between the contributing factors and the dependent variables: travel time and lane changing. PTV-VISSIM software was the main simulation tool used in this study. Each micro-simulation model was validated and calibrated for base conditions for each output: travel time (TT) and the number of lane changes (NLC). The author used factorial simulation and a hashing method to create all possible simulations by using the Python programming language. The final outputs were filtered to remove any redundant scenarios. After compiling inputs and outputs in a filtered and adjusted database, the author used the R programming language to conduct linear regression analyses. The results show that the main contributing factors to the number of lane changes aside from the through, left, and right turning volumes are the number of driveways, distance of the right turning lane to the upstream intersection, and the number of median openings. The results indicated that adding each driveway contributed to 54 more lane changes, while each median opening added 79 more lane changes per hour. Also, placing the start of the right turning lane closer to the first signalized intersection lead to fewer lane changes on the segment. The number of lane changes, the density of the driveways, segment length, and being located upstream to the freeway on-ramp contributed to higher travel times. The findings of this research provide designers and urban planners a deeper insight into the impact of design attributes on the operational performance of urban arterials near interchanges

Effect of Accelerated Artificial Aging on Translucency of Methacrylate and Silorane-Based Composite Resins

Objectives: Composite restorations must have tooth-like optical properties namely color and translucency and maintain them for a long time. This study aimed to compare the effect of accelerated artificial aging (AAA) on the translucency of three methacrylate-based composites (Filtek Z250, Filtek Z250XT and Filtek Z350XT) and one silorane-based composite resin (Filtek P90). Materials and Methods: For this in vitro study, 56 composite discs were fabricated (n=14 for each group). Using scanning spectrophotometer, CIE L*a*b* parameters and translucency of each specimen were measured at 24 hours and after AAA for 384 hours. Data were analyzed using one-way ANOVA, Tukey’s test and paired t-test at P=0.05 level of significance. Results: The mean (±standard deviation) translucency parameter for Filtek Z250, Filtek Z250XT, Filtek Z350XT and Filtek P90 was 5.67±0.64, 4.59±0.77, 7.87±0.82 and 4.21±0.71 before AAA and 4.25±0.615, 3.53±0.73, 5.94±0.57 and 4.12±0.54 after AAA, respectively. After aging, the translucency of methacrylate-based composites decreased significantly (P0.05). Conclusions: The AAA significantly decreased the translucency of methacrylate-based composites (Filtek Z250, Filtek Z250XT and Filtek Z350XT) but no change occurred in the translucency of Filtek P90 silorane-based composite. Keywords: Composite Resins; Silorane Resins; Methacrylate