Civil and Environmental Engineering

This paper presents a critical state constitutive model for cemented sand. The model uses a single capped yield surface as a function of the void ratio, confining pressure, preconsolidation pressure, and stress ratio at the peak of the undrained effective stress path. To model the cemented materials, the formulation of the yield function, elastic moduli, plastic modulus, flow rule, and other components of the model have been modified. Having incorporated the tensile strength and cohesion, the radial-mapping formulation of the bounding surface plasticity is incorporated in the model. The modified model has been calibrated and verified based on experimental results.

In recent years, there has been an increasing awareness of speeding as a significant road safety problem. Governments and agencies around the world are now emphasizing strategies to address speeding-related complaints in order to improve both actual and perceived levels of road safety. Several governments have taken steps to establish speed management programs to research speeding concerns and develop action plans. These programs manage speed by considering and optimizing the 3 E's of traffic safety (Education, Engineering, and Enforcement) and by adopting an evidence-based approach. The current approach to manage speeding complaints in different municipalities in Canada revolves around three main tasks: namely, tracking, investigating and resolving speeding complaints. Although the current process has many advantages, there is an increasing need to fortify a sophisticated system of speed datasets in order to address speeding complaints and to improve each of the three stages of the complaint process. Consequently, a framework for the future state of the speed complaint process was proposed.

Dhaka, the capital city of Bangladesh, is the largest and most industrialized  city with 15 million people. Due to rapid unplanned development, versatile land use,  rapid population growth, poor public transport system and increase of private car  users, traffic problems is worsening day by day. The only mass transit is bus which is insufficient in terms of safety, capacity, comfort and convenience. Considering the  worsening congestion it is high time to develop effective mass transit system such as  Bus Rapid Transit (BRT) as a means for achieving sustainable urban transport in the  city. In this paper an attempt has been made to propose a conceptual physical  structure of BRT for the line3 which starts from Uttara and ends in Ramna covering  around 18.5 km. The BRT stations and runways are designed in a way to satisfy the  ever increasing public transport demand towards achieving a sustainable urban public transport system.

Rather than investigate the isolated effects of individual weather elements on crash occurrence, this study investigates the aggregated effect of weather states, which are defined as a combination of various weather elements (i.e., temperature, snow, rain, and wind speed), on crash occurrence. The main argument is that a combination of weather elements might better represent a particular weather condition and subsequent safety outcome. Therefore, to explore the effect of various weather states on crash severity and type, this study defined 12 weather states, based on temperature, snow, rain and wind speed, and developed multivariate safety models using 11 years of daily weather and crash data for the entire City of Edmonton. The proposed models were estimated in a Full Bayesian context via a Markov Chain Monte Carlo simulation, while a posterior predictive approach was used to assess the models’ goodness-of-fit. Results suggested that Property-Damage-Only (PDO) crashes increased by 4.5%-45% due to adverse weather states. It was also shown that PDO crashes were more affected by adverse weather states compared to severe (injury and fatal) crashes. With regard to crash type, adverse weather states were associated with an increased occurrence of 9%-73.7% for all crash types, with the highest increase recorded for Ran-Off-Road (ROR) crashes. The duration of daylight hours was found to be significant and negatively related to all crash types and PDO crashes. In addition, sudden weather changes of major snow or rain were statistically significant and positively related to all crash types. Days-of-the-week (i.e., weekdays and weekend) and seasons-of-the-year (winter, spring, summer, and fall) were used as dummy variables and were statistically significant in relation to crash occurrence.

"Motivation: Previous research shows that various geometric and non-geometric road characteristics have significant effects on collision occurrence and severity on both highways and arterial roads; however, little is known about how these elements affect the safety performance of urban residential collector roads. Consequently, this study investigates the impact of these elements on collision occurrence and severity on urban residential collector roads.

Data and Methodology: An extensive data collection effort was conducted to synthesize collision record, traffic count, road geometry, traffic control and other feature data of residential collector road segments in Edmonton, Alberta, Canada. Using four years of collision data, negative binomial safety performance functions (SPFs) were developed for both collision occurrence and severity. The proposed models were estimated using the maximum likelihood estimation technique under an Empirical Bayesian approach. A backward stepwise procedure was used to select the model parameters, and an outlier test was performed to improve the models’ goodness-of-fit. Scaled Deviance (SD) and the Pearson X2 statistic were used to assess the models’ goodness-of-fit.

Results: Results reveal that the exposure covariates (segment length and traffic volume) are highly significant and positively related to predicted collisions in all of the SPFs. The Property Damage Only (PDO) collision model has the same significant covariates as the total collisions model, indicating that the number of PDO collisions is predominantly higher than other collisions. For predicted total and PDO collisions, there is a statistically significant positive relationship between collisions and access-point density, stop-controlled intersection density, the presence of a horizontal curve, the presence of a licensed premises, the presence of a seniors’ centre and the presence of on-street parking. By contrast, there is a significant negative relationship between predicted total and PDO collisions and the presence of a median. For severe (fatal and injury) collisions, there is a statistically significant positive relationship between collisions and segment length, traffic volume, number of lanes, access-point density, stop-controlled intersection density, bus stop density, the presence of a horizontal curve, the presence of a licensed premises, the presence of a seniors’ centre and the presence of on-street parking. On the contrary, there is a significant negative relationship between predicted severe collisions and the presence of a median, the presence of a centre line and the presence of manned enforcement sites.

Model Application: The city authority could use this information to assess the associated safety risks of different geometric and non-geometric characteristics of urban residential collector roads, and, hence, prioritize collision-prone road segments. "

"Motivation and Objectives:

“Complete Streets” is a relatively new transportation policy and design philosophy under which streets are planned and constructed to ensure safe access for all road users (i.e. pedestrians, motorists, bicyclists, etc.). However, there is a gap in the literature about how different road design features affect the safety performance of different Complete Streets cross-sections. Therefore, this study proposes a framework to assess the safety performance of alternative Complete Streets cross-sections on urban roadways based on the Highway Safety Manual (HSM) predictive method. The issues and challenges regarding the use of the HSM to perform this safety assessment are then discussed.

Methodology and Results:

The predicted number of collisions for alternative Complete Streets cross-sections was estimated using HSM base model, the Crash Modification Factors (CMF) of alternative cross-section design features, and the calibration factors. The calibration factors, used to replicate actual local roadway conditions, were derived using four years of collision data obtained from the city of Edmonton, Alberta, Canada. The CMFs were collected through an extensive literature review. The results obtained from the calibrated HSM model reveal that road cross-sections with a large lane width, a large offset of a roadside fixed object, the presence of median, no on-street parking, and no on-street bike lane have less safety risks compared to road cross-sections that do not possess these features.

Issues and Challenges:

While performing the safety assessment through the HSM methodology, several issues and challenges were faced: i) for urban roadways, the HSM focuses only on arterial roadways; no guideline is provided for urban collector nor local roadways; ii) there is a lack of HSM base models for certain roadway types; iii) base conditions were difficult to transfer and calibration factors lacked the strength to replicate actual local roadway conditions; iv) appropriate and (or) exact CMFs for specific road design features were difficult to find in the literature, and most of the CMFs were developed for highways, rural roadways, or urban arterials and focused on certain collision types or severity. The available CMFs from other jurisdictions may not be applicable to replicate actual local roadway conditions; therefore, various assumptions were made in the analysis to determine the CMFs for specific road design features.

Research Scope:

The framework proposed herein can be proactively used during roadway planning and design to assess the associated safety risk of different Complete Streets cross-sections. Furthermore, the issues and challenges faced while adopting HSM may provide a future research direction to enhance the scope of the HSM."