Driving Information in a Transition to a Connected and Autonomous Vehicle Environment: Impacts on Pollutants, Noise and Safety

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Can turbo-roundabouts and restricted crossing U-Turn be effective solutions for urban three-leg intersections?

This research explored the potential of replacing conventional single-lane roundabouts by turbo-roundabouts and yield- and stop-controlled restricted crossing U-Turn (RCUT) at intersections located in urban corridors. A simulation approach based on a well-integrated assessment of traffic performance, emissions and driving volatility indicators of alternative intersection designs (AIDs) is therefore a major contribution of the study. The paper also addressed the impacts that several locations of the U-Turn crossovers have on travel and idling times, as well as on carbon dioxide and nitrogen oxides emissions. Traffic, pedestrian, and cyclist flow data were collected from two urban three-leg single-lane roundabouts. A microscopic simulation platform of traffic and emissions (respectively, VISSIM and vehicle specific power) was used to evaluate intersection-specific design and operations. The results indicated that turbo-roundabout and yield-controlled RCUT outperformed the existing single-lane roundabout at the two sites. Turbo-roundabout generally yielded the lowest travel times and emissions compared to the other intersections. The Yield-RCUT also performed better than the single-lane roundabout for U-Turn crossover located 100–170 m from the main intersection. Our findings bring a solid basis for academic research and transportation planners to promptly consider the implementation of AIDs and contribute to sustainable mobility in cities.publishe

Safety and emissions algorithms for the interaction between motor vehicles and vulnerable road users

Road traffic has been responsible for high levels of pollutant emissions, several injuries and deaths. Many studies have been focused on safety or emissions issues, but an integrated approach considering safety-emission hotspots is rather rare, particularly, with respect to impacts involving Vulnerable Road Users (VRU), such as pedestrians and cyclists. The recent advancements in technology and in vehicle automated functions will reshape the road traffic environment, and soon, there will be a transition phase where Conventional Vehicles (CVs) and Connected and Autonomous Vehicles (CAVs) will coexist and share the road infrastructure. Therefore, this Ph.D. research seeks to develop an integrated approach focused on advanced algorithms to reduce driving behavior volatility through safety and emissions warnings in an urban environment focusing on the transition phase. Real data will be used to evaluate driving volatility and pollutant emissions. Safety and emissions will be combined through an integrated methodology under a statistics-optimization-data mining framework. The expected contributions of this Ph.D. research will be: 1) a thorough and microscopic characterization of individual driver decision mechanisms focused on safety and emissions hotspots in urban areas, with a major concern on VRU exposure; 2) a tool of driver warning and control assistance mechanism to be applied in both CVs and CAVs.publishe

Integrated impact assessment of shares, automated and electric mobility

Major transformations in the road transportation sector such as vehicle automation, electrification, and shared mobility, create opportunities to tackle sector challenges. Despite the promising positive impact, little is known about the real potential and the effective sustainability of a combination oh these emerging mobility systems. The proposed doctoral research plan intends to understand and quantify the environmental and energy-related impacts of shared, fully automated, and electric mobility. A fundamental understanding of the upstream and downstream environmental impacts of a product and a system considering SAEVs fleet adjusted to different travel demands will be conducted in a life cycle assessment (LCA) approach. The assessment of potential environmental impact reduction has always been a research hotspot; however, most studies are only focused on operational impact. Moreover, the impact of SAEVs in the road network considering presence, routing, location, access to charging stations and scheduling will be addressed. Hence, automated driving decisions and distinguishing normal from recurring driving patterns are required to develop a framework for generating an automated mobility service. Attention will be given to the application of SAE mobility both at urban and inter-urban scales. The evaluation of the impacts of emerging mobility systems requires a comprehensive set of criteria. Results of the research intend to culminate into a feasibility study combining environmental, economic, and consumer perspective viability of the examined systems. The main research questions of this study are: 1) Which routing strategies should be adopted for energy-efficient driving decision?; 2) What are the impacts of SAEVs systems through a life cycle concept?; 3) What is the potential of SAEVs to manage traffic demand at urban and interurban scales?publishe

Driving Information in a Transition to a Connected and Autonomous Vehicle Environment: Impacts on Pollutants, Noise and Safety

The main objective of this vision paper is to present the project “DICA-VE: Driving Information in a Connected and Autonomous Vehicle Environment: Impacts on Safety and Emissions”, which aims to develop an integrated methodology to assess driving behavior volatility and develop warnings to reduce road conflicts and pollutants/noise emissions in a vehicle environment. A particular attention will be given to the interaction of motor vehicles with vulnerable road users (pedestrians and cyclists). The essence of assessing driving volatility aims the capture of the existence of strong accelerations and aggressive maneuvers. A fundamental understanding of instantaneous driving decisions (through a deep characterization of individual driver decision mechanisms, distinguishing normal from anomalous) is needed to develop a framework for optimizing these impacts. Thus, the research questions are: 1) Which strategies are adopted by each driver when he/she performs short-term driving decisions and how can these intentions be mapped, in a certain road network?; 2) How is driver’s volatility affected by the proximity of other road users, namely pedestrians or cyclists?; 3) How can driving volatility information be integrated into a platform to alert road users about potential dangers in the road infrastructure and prevent the occurrence of crash situations?; 4) How can anomalous driving variability be reduced in autonomous cars, in order to prevent road crashes and have a performance with a minimum degree of emissions? This paper brings a literature review on this topic and an evaluation of methods that can be used to assess driving behavior patterns and their influence on road safety, pollutant and noise emissions.publishe

A study on vehicle Noise Emission Modelling: correlation with air pollutant emissions, impact of kinematic variables and critical hotspots

This work proposes a methodology suitable for analysing the sound power levels (Lw), and carbon dioxide (CO2) and nitrogen oxides (NOx) emissions along a travel, and consequentially assessing the related critical hotspots. The estimation of noise and pollutant emissions from six vehicles driven along three different routes (one National Road and two highways) was conducted, in combined way, through seven Noise Emissions Models (NEMs) and Vehicle Specific Power (VSP) methodology, respectively. The inputs required by the models (namely, vehicle speed and acceleration and road grade) were extrapolated from On-Board Diagnostic (OBD) system and Global Positioning System (GPS) data recorded during monitoring campaigns. The specificities of each model were analysed, and the role played by the kinematic variables in noise and exhaust emissions assessment was highlighted. Results show that all the tested NEMs estimated higher noise levels on the highways, while VSP predicted higher emissions on the National Road. This happens because speed is the main input variable in NEMs, while acceleration has an impact on noise estimation in the low-speed range (below 50 km/h). For pollutant emissions evaluation, acceleration plays a fundamental role also at high-speed range, where a transition from a cruising condition to an acceleration phase leads to significant variations in terms of VSP values. Lw values, estimated with NEMs that use acceleration correction terms, present positive moderate-to-high correlation with VSP ones. Moreover, the models that neglect acceleration in noise estimation fail to recognize traffic control treatments as critical hotspots.A. Pascale acknowledges the support of FCT for the Scholarship 2020.05106.BD.publishe

Micro driving behaviour in different roundabout layouts: pollutant emissions, vehicular jerk, and traffic conflicts analysis

Driving behaviour affects both road safety and the environment, either positively or negatively. An unsafe driving behaviour characterized by hard acceleration/braking (also called driving volatility) can lead to an increase in emissions. Driving volatility can occur due to driving style, traffic, or road conditions. Although roundabouts present better safety performance than other traffic-control treatments, different layouts may lead to different levels of traffic-related impacts. This paper aims to evaluate vehicle movements through three types of roundabouts (Single-lane (SL), Compact two-lane (CTL), and Multi-lane (ML)) focusing on assessing the impact of driving volatility on traffic conflicts and pollutant emissions. A micro driving behaviour analysis of emissions, driving volatility, and conflicts were conducted for the links of the entry, circulating, and exit areas of the studied roundabouts. Speed was used as a variable parameter directly related to the driver while vehicular jerk and traffic conflicts, as well as global (carbon dioxide – CO2) and local (nitrogen oxides – NOx) pollutants were used to evaluate the traffic safety and emissions performance, respectively. Field measurements obtained from a light-duty probe vehicle equipped with an on-board diagnostic reader on three different layout roundabouts located in suburban environments were used to develop a microscopic traffic simulation for the baseline. Simulations were conducted using VISSIM, emissions were estimated using the Vehicle Specific Power (VSP) methodology, and the Surrogate Safety Assessment Model (SSAM) was applied for estimating the traffic conflicts between motor vehicles. Four speed-distribution scenarios were considered, and associated impacts were evaluated for each roundabout. In general, speed variation and subsequently vehicular jerk had more impact on traffic conflicts than pollutant emissions. The number of conflicts in the exit area was less than entry and circulating in all roundabout designs but ML presented more traffic conflicts.publishe

Should future cities be compact or sprawled? development of an eco-indicator to assess future urban planning strategies

Urban planning strategies can help mitigate climate change effects in cities and improve the quality of cities environment by providing a more sustainable development. However, there is still a debate on whether cities should be compact or sprawled. This study aims to develop an eco-indicator to assess parameters affected by urban morphology -air quality, urban heat fluxes, urban heat island, mobility, ecological footprint and human exposure - to evaluate the most sustainable urban planning strategies under future climate. For that, a numerical modelling approach will be applied, including the WRF-UCM-CAMx air quality modelling system, adapted to urban areas with high spatial detail, the traffic model VISUM, and a carbon balance, for the Aveiro Region case study. Three urban morphology scenarios will be developed to assess the effects of urban planning strategies. The first scenario will represent the compact city, composed of several independent cores, where commuting outside each city core is not a necessity (sustainable cities). The second scenario will represent the same cores, but in this scenario, commuting is required (polycentric city). The third scenario will represent the dispersed city, without any core areas. All the scenarios will be compared with a reference scenario, which will consider the current urban morphology. Emissions for each scenario will be estimated, based on the land use changes imposed by each urban morphology, in three main activity sectors: transportation, residential combustion and industry. All scenarios will consider the average future technological mobility changes (i.e., car-sharing) for the future medium-term. The main contribution from this research, the eco-indicator, will serve both decision maker and research communities, overcoming the existing gaps in this scientific field and supporting the best planning strategies for a healthy environment and wellbeing.publishe

The relevance of on-road emission monitoring in different type of roundabouts in rural roads

Road traffic significantly contributes to urban air pollution as means of particulate matter (PM) and nitrogen oxides (NOX) emissions [1]. Despite the deployment of clean powertrains, internal combustion engines are the most widely used technology in the European Union; gasoline- and diesel-fueled represented around 90% of passenger cars sold between 2014 to 2017 [2]. The amount of exhaust gases emitted by motor vehicles depend on speed profile, vehicle type, traffic volumes and intersections [3]. Roundabouts have been considered and built around the world to replace intersections previously controlled by traffic lights as a means of improving operational performance, at least in certain flow range [4]. These latter ones are considered pollution hotspots locations, due to speed changes cycle around them [5] [6]. Despite the demonstrated benefits in terms of traffic flow, delay reducing and safety [7], roundabouts raised some doubts concerning emissions performance [8]. Bearing this in mind, this paper compares vehicle activity and on-road emission data in three different roundabouts in rural roads: a compact two-lane, a multi-lane and a single lane roundabout in Aveiro, Portugal. It was hypothesized that carbon dioxide (CO2) and NOx emissions, engine speed and the relative positive acceleration (RPA) are impacted by the differences in the approaching and conflicting traffic volumes, the volume-to-capacity ratio and the roundabout layout. Input data such as approaching and circulating traffic volumes, and queue length were collected by videos cameras installed at the studied locations. Field measurements were carried out with two light duty vehicles (gasoline and diesel), using a Portable Emissions Measurement System (PEMS) to measure CO2 and NOX volumetric concentrations. Alongside, an OBD-II scan interface record vehicle speed data, engine speed and acceleration. After that, a relationship between congestion level of roundabouts and occurrence of each speed profile (no stop – I, stop once – II and multiple stops – III) was established, using discrete choice models. Finally, discrete choice models obtained from single-lane, compact two-lane and multi-lane roundabouts were compared. The methodology and models developed used in this paper can be applied by simply measuring roundabout traffic volumes by means of discrete choice models that allows simultaneously detecting differences in location and variability characteristics of the distributions of the observations taken at roundabouts. It also allows to identify some relevant operational and design features of a rural roundabout prior its implementation to enhance capacity and emissions fields.publishe