Average Road Research Articles

The impacts of road network density on motor vehicle travel: An empirical study of Chinese cities based on network theory

Abstract This paper examines the impacts of road network density on motor vehicle travel through traffic flow and network analysis of cities in China from three perspectives: multi-city comparison with traffic flow data, multi-city and multi-period comparisons with structural characteristics. When we examine the correlation between road network density and traffic flow characteristics including the travel time and speed of 35 major cities in China, no correlation exists between them which may result from different network structures, dynamic traffic demands, traffic control plans, driving behaviors, and so on. It inspires us to explore the correlation between road network density and static travel indicators. Then structural characteristic of road networks can be treated as a fixed relatively attribute and becomes the next research emphasis of this work. Comparative analysis results of three current cities (Xiamen, Washington D.C., San Jose) indicate that the average travel distance in different cities with the similar land area will not increase significantly as road network density increases. Results of an analysis of road network evolution of Changchun, China show that the increase of road network density shortens the average road segment length as well as travel distance in general. This impact on average travel distance is also related to evolution periods or modes of urban road networks. These findings provide important empirical support for planners and policymakers to understand the impacts of road network density on transport performance and design more effective urban road networks.

Deicing performances of a road unit driven by a hydronic heating system in severely cold regions of China

The deicing performances of a road unit driven by a hydronic heating system in severely cold regions of China were investigated by using the Open Source Lattice Boltzmann Code. The model used the enthalpy-based method and double distribution functions for the velocity and temperature fields to solve the ice melting problem. The average road surface temperatures and melting conditions (melting ratio and mass) as affected by ice thickness (3 ∼20 mm), pipe spacing (80 ∼240 mm), and air temperature (252 ∼268 K) were detailed, and the parameters were analyzed by the orthogonal test method. The results show that for the ice thickness increasing from 3 mm to 20 mm, the heating rate was slightly increased from 6.3 K/h to 6.45 K/h in the preheating and initial melting stages, and from 1.32 K/h to 2.06 K/h in the rapid melting stage, the melting mass was increased from 360 g/m to 762.06 g/m whereas the melting ratio was decreased from 1.00 to 0.32. The pipe spacing of 120 mm was suitable for the road heating whereas ≥ 160 mm was not feasible in the severely cold regions. For the air temperature was increased from 252 K to 268 K, the preheating time was decreased from 3.02 h to 0.82 h, the heating rate in the melting stages was increased from 0.68 K/h to 2.94 K/h and the melting ratio was linearly increased. The parameter analysis reveals that the air temperature had the most important influence on the melting ratio whereas the pipe spacing had the most significant impact on the average road surface temperature, and the ice thickness had a slight influence on the melting ratio and average road surface temperature.

Real emissions, driving patterns and fuel consumption of in-use diesel buses operating at high altitude

We report simultaneous measurements of fuel consumption, driving patterns, and CO2, CO, and NOx emission factors for diesel passenger buses under real operating conditions in high altitude cities (>2000 masl) and in mountainous regions with an average road grade of 4%. These measurements were obtained using a Portable Emission Measurement System (PEMS) monitoring a sample of 15 buses during eight months of daily operation. For a city with a high level of vehicular traffic (Mexico City), we obtained an average fuel consumption of 0.41 L/km and emission factors of 965.8, 41.4, and 5.3 g/km for CO2, CO, and NOx, respectively. Fuel consumption and CO2 emissions were within expected values. However, CO emissions were approximately three times higher while the NOx emission were half of the reported values in the literature for buses of similar technology working at low altitude.

Perspectives on Electrification for the Automotive Sector: A Critical Review of Average Daily Distances by Light-Duty Vehicles, Required Range, and Economic Outcomes

This paper aims at providing a multisource data analysis, including direct data collection, focussed on daily average distances covered with motorized mobility. Its results can be used as a basis for policies involving a shift towards new propulsions, electric motors or hybrid electric vehicles (HEV) for road vehicles. A number of variables influence the propensity of drivers to use electric traction, even the option of plug-in hybrid electric vehicles (PHEV). This paper addresses one of these variables: the compliancy of electric traction—regarding both hybrid plug-in solutions and full-electric vehicles, in addition to the autonomy of batteries (range)—with the daily travels by road vehicles, mainly by automobiles. We want to understand whether the constraints leading towards a greater independence from crude oil rather than constraints concerning emissions, mainly in urban contexts, might be compliant with the habitual daily trips of drivers. We also want to understand if these daily trips have varied much during recent years and the consequences they may have on operational costs of plug-in automobiles. After introducing a general overview of road-motorized mobility in Italy, the paper compares data from other studies to provide an indication of average daily driving distances. This reveals how different recent analyses converge on a limited range of average road distances covered daily by Italians, which is compliant with ranges allowed by electric batteries, provided that their low energy density in comparison with that of oil-derived fuels do not arrive to imply a significant increase in vehicle mass. Subsequently, average distances in some EU countries are taken from the literature, and the results are also compared with U.S. data. The study extends the analysis of trends on the use of automobiles and road-vehicles to the international context by also addressing average daily distances covered for freight transport in some EU countries, thereby providing a further basis for comparison and for understanding whether the daily motorized mobility can be considered as a stable phenomenon. Finally, an analysis is provided of the economic operational advantages from using plug-in vehicles.

A traffic-aware electric vehicle charging management system for smart cities

The expected increase in the number of electric vehicles (EVs) in the coming years will contribute to reducing CO2 pollution in our cities. Currently, EVs' users may suffer from distress due to long charging service times and overloaded charging stations (CSs). Critical traffic conditions (e.g., traffic jams) affect EVs' trip time (TT) towards CSs and thus influence the total trip duration. With this concern, Intelligent transport systems (ITS) and more specifically connected vehicle technologies, can leverage an efficient real-time EV charging service by jointly considering CSs status and traffic conditions in the city. In this work, we propose a scheme to manage EVs' charging planning, focusing on the selection of a CS for the energy-requiring EV. The proposed scheme considers anticipated charging slots reservations performed through a vehicular ad hoc network (VANET), which has been regarded as a cost-efficient communication framework. In specific, we consider two aspects: 1) the EV's total trip time towards its destination considering an intermediate charging at each candidate CS, and 2) the communication delay of the VANET routing protocol. First, in order to estimate the EV's total trip time, our CS selection scheme takes into account the average road speed, traffic lights, and route distance, along the path of the EV. The optimal CS that produces the minimum total charging service time (including the TT) is suggested to that energy-requiring EV. Then, we introduce two communication modes based on geographical routing protocols for VANETs to attain an anticipated charging slot reservation. Simulation results show that with our charging scheme EVs' charging service time is reduced and more EVs are successfully charged.

Development of the Road Network in the City of Salt in 2004 and 2016 Using GIS

The aim of this study is to analyze the structure of the road network in As-Salt City in the period between 2004 and 2016, in order to identify the road employability in terms of the degree of connectivity, rotation, accessibility, and density. The relationship between the social properties and road distribution are also examined through analysis of the network characteristics concerning population distribution. The data used in this study was based on the As-Salt City Municipality Database supported with fieldwork done in 2016. The network analysis approach using GIS was used to calculate the roads employability.
 
 The study compares between the results of the analysis using the cognitive model of the road network for the years 2004 and 2016, knowing that the number of nodes in 2004 and 2016 was constant indicating the number of neighborhoods is 20, while the number of links changed from 42 links in 2004 to 50 links in 2016 and the average center of roads was determined, and it was estimated that the average road center is located near the municipality of As-Salt
 
 The study indicates that the road network suffers from a low degree of communication and rotation and the standard distance of road sites in the study area. The standard distance for each group was 2338.49 m. There is a disparity in the distribution of road network within As-Salt City, and the proportion of roads lengths dose not suit the population distribution pattern. The neighborhood of Al- Salalem, includes 19.5% of the total number of roads in As-Salt, because the neighborhood of Al-Salalem contains the highest population census and this is accompanied by urban growth, which is necessarily accompanied by the presence of roads. Therefore, it is recommended to have a plan to redistribute the population in the city and to establish new roads to reduce the problems of traffic in the city.

Economic Analysis of Crack Treatment Methods Using HDM-III Modeling

Crack sealing treatment includes the use of a router to create a reservoir on the intended cracks, whereas crack filling is given without any modification to the crack wall. With sealing treatment the pavement can have longer service period because of its good adhesion and cohesion performance. However, the initial cost of sealing is higher due to the use of extra material, equipment and labor. As a result, the aim of this study is to investigate the long-term cost-effectiveness in between these two treatment techniques in Texas and to observe if the longer service period can compensate the higher initial cost of sealing treatment. For this purpose, the initial cost inputs have been identified and a highway design and maintenance standard model (HDM-III) used to evaluate the most cost-effective pavement maintenance between crack sealing and filling treatment over a 25-year analysis period. Agency, capital and net present value have been calculated by using HDM-III based upon average daily traffic (ADT), altitude and road length. The results of this study indicated that (1) crack sealing is more cost-effective pavement maintenance compared to crack filling over a long period of time; (2) agency cost can be reduced by 15% and 14% based on ADT and road length analysis, respectively, by implementing crack sealing treatment; (3) capital cost in terms of ADT and road length with crack sealing maintenance can be saved by 24% and 19%, respectively; (4) the net present value with crack sealing treatment after a 25-year analysis period is higher for ADT and road length compared to crack filling by 18% and 19%, respectively; (5) the cost-effective resealing interval years of 5 years is proposed when the unit cost of routing increased by 25%.

Determining the priority criteria and ranking of provincial bridge maintenance in West Sumatra using a combination of the Fuzzy Analytical Hierarchy Process and VIKOR-Modification methods

There are many bridges that need to be maintained in a provincial road network, with limited funds for bridge maintenance, many bridge criteria (average daily traffic, economic benefits, fund budget, technical conditions, bridge hierarchy, spatial planning, flood potential, type of damage, erosion potential, age and surface concrete, etc.), and various levels of conditions, are a number of criteria that are taken into account in the decision making by the government as an institution responsible for the functioning of roads and bridges. The selection of bridge maintenance priorities in West Sumatra Province was decided through a coordination meeting between agencies, and sometimes relatively without going through sufficient technical analysis. This research initiated, the selected criteria to be taken into consideration, the order of the important criteria in the selected network segment. This study involved a number of road and bridge maintenance experts at the Ministry of Public Works, Road and Bridge Research and Development Institutions, as well as the Department of Public Works and Spatial Planning of West Sumatra Province. A combination of Fuzzy Analytic Hierarchy Process (to determine weighted criteria) and VIKOR-Modification methods (to determine the order of choice of bridges to be handled) are selected. There are eight criteria that can be used in determining the priority of bridge maintenance, and the priority sequence of the most important are: bridge technical conditions, aging of the bridge, average daily traffic, economic benefits, road function, budget, disaster risk (Flood, Landslides, Tsunamis) and Spatial Plans.

Route Control Strategies for Autonomous Vehicles Exiting to Off-Ramps

This paper proposes three route control strategies for autonomous vehicles (AVs) exiting to off-ramps. First, two microscopic lane-changing models are developed to simulate the off-ramp behaviors for AVs. A risk factor $\lambda $ is introduced in the discretionary lane-changing (DLC) model, and a five-step process is developed for the mandatory lane-changing (MLC) model. Second, three route control strategies are presented, i.e., grading strategy (GS), half-overlap strategy (HOS), and full-overlap strategy (FOS). Finally, the extensive numerical simulations are conducted to analyze the characteristics of each strategy based on the MATLAB platform. The results indicate that the studied area displays significant variability in spatiotemporal dynamics of average velocity and road capacity under different strategies. It is found that the GS is the most effective control strategy for traffic congestion dissipation and travel delay reduction, followed by the HOS and, then, the FOS. The road capacity under the GS is increased by 19.1% and 7.8% compared to the FOS and the HOS, respectively. Furthermore, the GS consumes lower costs in terms of safety, travel efficiency, and route and lane switch frequency compared to the HOS and FOS, which is verified as the optimal strategy according to overall running cost. The findings of this paper can provide useful references for the design of AVs as well as the management of the automated highway systems.

Application of land-use regression models to estimate sound pressure levels and frequency components of road traffic noise in Taichung, Taiwan

Few studies have applied land-use regression to predict road traffic noise exposure, and there are few predictive models for different frequencies. This study aimed to measure 24-h average road traffic noise levels and to analyze the frequency components over one year to establish land-use regression models of noise exposure. Fifty monitoring stations were set up to conduct 3 measurements for A-weighted equivalent sound pressure levels over 24 h (Leq,24h) and night equivalent sound pressure levels (Lnight), as well as octave-band analyses, during the 2013–2014 period. Noise measurements were integrated with land-use types, road and traffic information, meteorological data and geographic information systems to construct land-use regression models. Leave-one-out cross-validation was performed to test the validity of the predictive models. The annual means of Leq,24h and Lnight were 66.4 ± 4.7 A-weighed decibels (dBA) and 62.1 ± 6.0 dBA, respectively. Octave-band frequency analyses revealed that the highest means over 24 h and at night were 61.4 ± 5.3 decibels (dB) and 56.7 ± 6.6 dB (both at 1000 Hz), respectively. The model-explained variance (R2) of the full-frequency noise was 0.83 for Leq,24h and 0.79 for Lnight. The R2 values for octave-band-frequency noise ranged from 0.67 to 0.88 for Leq,24h and 0.65 to 0.85 for Lnight, with the highest R2 at 250 Hz for Leq,24h and at 125 Hz for Lnight. The differences between the model R2 and the leave-one-out cross-validation R2 ranged from 5% to 15% for both Leq,24h and Lnight at all frequencies. In the validation, the root mean squared error was 2.09 dBA and 2.80 dBA for the full-frequency Leq,24 and Lnight, respectively, and ranged from 1.89 to 2.62 dB and from 2.51 to 3.28 dB for the octave-band-frequency Leq,24h and Lnight, respectively. This study observed that the annual means of the measured Leq,24h and Lnight in Taichung were both above 60 dBA and had the highest level at 1000 Hz. The developed land-use regression models of Leq,24 and Lnight both had good predictive capacity for the full frequency spectrum and within octave bands and can therefore be applied for epidemiological studies.

Road traffic accident severity analysis: A census-based study in China

Background: In China, despite the decrease in average road traffic fatalities per capita, the fatality rate and injury rate have been increasing until 2015. Purpose: This study aims to analyze the road traffic accident severity in China from a macro viewpoint and various aspects and illuminate several key causal factors. From these analyses, we propose possible countermeasures to reduce accident severity. Method: The severity of traffic accidents is measured by human damage (HD) and case fatality rate (CFR). Different categorizations of national road traffic census data are analyzed to evaluate the severity of different types of accidents and further to demonstrate the key factors that contribute to the increase in accident severity. Regional data from selected major municipalities and provinces are also compared with national traffic census data to verify data consistency. Results: From 2000 to 2016, the overall CFR and HD of road accidents in China have increased by 19.0% and 63.7%, respectively. In 2016, CFR of freight vehicles is 33.5% higher than average; late-night accidents are more fatal than those that occur at other periods. The speeding issue is severely becoming worse. In 2000, its CFR is only 5.3% higher than average, while in 2016, the number is 42.0%. Conclusion and practical implementation: A growing trend of accident severity was found to be contrasting to the decline of road traffic accidents. From the analysis of casual factors, it was confirmed that the release way of the impact energy and the protection worn by the victims are key variables contributing to the severity of road traffic accidents.

Soil erosion of unpaved loess roads subjected to an extreme rainstorm event: a case study of the Jiuyuangou watershed on the Loess Plateau, China

Rainfall can cause serious soil loss in the Loess Plateau hilly and gully region, but little focus has been placed on the extreme rainstorm effects on unpaved loess road soil erosion. A field survey method was used to investigate the erosional effects of the “7.26” heavy rainfall event on unpaved loess roads in the Jiuyuangou watershed of the Loess Plateau, China. The results showed that the average and maximum widths of the eroded gullies that formed on the unpaved roads were 0.65–1.48 m and 1.00–3.60 m, respectively. The average and maximum depths of the eroded gullies were 0.42–1.13 m and 0.75–4.30 m, respectively. The average width-to-depth ratio was 1.31, indicating that the widening effect was greater than the downcutting effect in the eroded gullies. In addition, the gully density ranged from 0.07 to 0.29 m m−2, and the road surface dissection degree ranged from 0.03 to 0.41 km2 km−2. Eroded gullies generally developed at the slope toe of the cut bank side. The average eroded gully width and depth at turns in the road were 1.47–2.64 times and 1.30–3.47 times greater, respectively, than those in other road sections. The road erosion modulus increased from the upper section to the lower section of the roads. The average road erosion modulus of the study catchment was 235,000 t km−2. Turns in the road were associated with collapses, sinkholes and other gravitational erosion phenomena. The amount of road erosion under extreme rainfall conditions is mainly related to the interactions among road length, width, slope and soil bulk density. Our results provide a useful reference for developing further measures for preventing road erosion on the Loess Plateau.

Engaging minibus taxi drivers in the quest for child safer roads

South Africa has double the world average child road fatality rate, with at least 1 300 children killed every year. A leading contributor to this public health challenge is the lack of safe public transport that enables children to reach schools easily. Minibus taxis (MBTs), South Africa’s incarnation of paratransit services, have aimed to fill this gap by providing transport at a reasonably priced fare and a relatively higher frequency, compared with other modes of public transport. However, the informal nature of MBTs means that this form of transport places passengers at a relatively higher risk of road accidents due to the use of unroadworthy vehicles, reckless driving and speeding. This paper provides an overview of the Safe Travel To School (STTS) programme, which was initiated in 2014 with a view to providing a localised intervention that would potentially strengthen the safety of MBTs for scholar transport in South Africa. The programme aims to provide safer travel for child passengers by monitoring driver performance through a tracking device installed in each vehicle and rewarding good driver performance each quarter. A driver recruited into the programme also undergoes health tests and training that covers first aid, defensive driving and road safety training. The literature review that each of these components improves driver performance. A previous evaluation of the programme found that since inception, drivers in the programme have shown better driving performance than general motorists. Thus, the STTS programme potentially provides an implementable practice model for safe scholar transport that is oriented towards a developing country like South Africa.

Long-Term Exposure to Road Traffic Noise and Incidence of Diabetes in the Danish Nurse Cohort.

Background:Evidence on the association between road traffic noise and diabetes risk is sparse and inconsistent with respect to how confounding by air pollution was treated.Objectives:In this study, we aimed to examine whether long-term exposure to road traffic noise over 25 years is associated with incidence of diabetes, independent of air pollution.Methods:A total of 28,731 female nurses from the Danish Nurse cohort ( at recruitment in 1993 or 1999) were linked to the Danish National Diabetes Register with information on incidence of diabetes from 1995 until 2013. The annual mean weighted levels of 24-h average road traffic noise () at nurses’ residences from 1970 until 2013 were estimated with the Nord2000 method and annual mean levels of particulate matter (PM) with diameter and ( and ), nitrogen dioxide (), and nitrogen oxide () with the Danish AirGIS modeling system. Cox proportional hazards regression models were used to examine the association between residential in four different exposure windows (1-, 5-, 10-, and 25-years) and the incidence of diabetes, adjusted for lifestyle factors and air pollutants.Results:Of 23,762 nurses free of diabetes at the cohort baseline, 1,158 developed diabetes during a mean follow-up of 15.2 years. We found weak positive associations between 5-y mean exposure to (per increase) and diabetes incidence in a crude model [hazard ratio (HR): 1.07; 95% confidence interval (CI): 0.99, 1.12], which attenuated in a model adjusted for lifestyle factors (HR:1.04; 95% CI: 0.97, 1.12), and reached unity after additional adjustment for (HR: 0.99; 0.91, 1.08). In analyses by level of urbanization, we found a positive association between noise and diabetes in urban areas (HR:1.27; 95% CI: 0.98, 1.63) that was unchanged after adjusting for (HR: 1.25; 95% CI: 0.97, 1.62), but we found no apparent association in provincial (HR: 1.02; 95% CI: 0.88, 1.18) or rural areas (HR: 0.97; 95% CI: 0.87, 1.08). Conclusion:In the nationwide cohort of Danish nurses 44 years of age and older, we found no association between long-term exposure to road traffic noise and diabetes incidence after adjustment for but found suggestive evidence of an association limited to urban areas. https://doi.org/10.1289/EHP4389

Size Distribution of Building Lots and Density of Buildings and Road Networks: Theoretical Derivation Based on Gibrat’s Law and Empirical Study of Downtown Districts in Tokyo

The concept of density lacks the ability to explain the diversity of physical elements of urban form such as building lot sizes. Thus, urban planners tend to discuss the validity of density values without taking into consideration the variation of building lot sizes due to the limited data available on building lot shapes. Our objective is to discuss the potential of building density and road network density in order to estimate the size distribution of building lots at the district scale in downtown Tokyo. The study finds that (1) building lot sizes approximately follow the lognormal distribution whose parameters, mean, and variance are formulated by gross building density, the coefficient of variation of building lots, road network density, and average road width by removing large building lots and (2) the value of the coefficient of variation is approximately equal to one. As a practical problem, we discuss how to determine the maximum building density by considering the variation of building lot sizes. It was found that the maximum building density can be determined based on a stochastic approach. These findings are expected to provide urban planners with a theoretical basis for discussing the validity of density values.

Forty years later: Assessment of the long-lasting effectiveness of land consolidation projects

The high cost of implementing land consolidation projects (LCPs) justifies investigation of the question about the duration of economic effects of farmland merging. The assessment of economic effectiveness of LCP can be an essential argument in budgeting proceedings and in discussion of the importance of land relocation in the sustainable development of rural areas.The main aim of this research was to verify the hypothesis of persistence of favourable basic parameters of land fragmentation (LF) and other factors affecting the efficiency of agricultural production that are still observed even several decades after LC. The aim was also to confirm that the parameters of LF within merged area are still much more favourable than those in neighbouring areas that have never been subjected to LC. The additional goal was to determine the scale and intensity of changes in LF that took place after farmland merging, and to estimate the influence of LC to farmland abandonment by analysing the intensity of secondary forest succession. The research was focused on the Jabłonka commune located in the southern Poland.The results demonstrated the long-lasting effects of farmland merging, which are still evident even 40 years after the project has been completed. This is the most evident regarding the average plot size, road accessibility and land fragmentation indicators, which are calculated based on the area of the land parcel. Additionally, within the merged village the lowest level of land abandonment was observed, which was indicated by analysis of the areas covered by secondary forest succession and afforestation processes within formerly agriculturally areas. The results clearly indicated a multi-generational and positive impact of LCP on the development and functioning of rural areas.

Urban emission inventory optimisation using sensor data, an urban air quality model and inversion techniques

An optimisation scheme has been developed that applies a Bayesian inversion technique to a high resolution (street-level) atmospheric dispersion model to modify pollution emission rates based on sensor data. The scheme minimises a cost function using a non-negative least squares solver. For the required covariance matrices, assumptions are made regarding the magnitude of the uncertainties in source emissions and measurements and the correlation in uncertainties between different source emissions and different measurement sites. The scheme has been tested in an initial case study in Cambridge using monitored data from four reference monitors and 20 AQMesh sensor pods for the period 30 June 2016 to 30 September 2016. Hourly NOx concentrations from road sources modelled using ADMS-Urban and observed concentrations were processed using the optimisation scheme and the adjusted emissions were re-modelled. The optimisation scheme reduced average road emissions on average by 6.5% compared to the original estimates, changed the diurnal profile of emissions and improved model accuracy at four reference sites.

Limited Knowledge of Safe Driving Practice among Drivers with Diabetes in Armenia: Association with Greater Risk of Motor Vehicle Accidents

Aims: The aims of the study were to assess the degree of knowledge and adherence to the recommended safe practice for driving and the risk of road traffic accidents among people with diabetes mellitus in Armenia. Methods: A total of 628 respondents, including 200 drivers, out of 641 consecutive attendees at six diabetes clinics, participated in the survey. A modified British questionnaire on driving and diabetes was used to obtain the relevant data. The information from all 103 drivers treated with insulin and 73 taking sulfonylureas was reviewed. Results: The study revealed that of 176 insulin and sulfonylurea-treated drivers, 161 (91.5%) had never received any advice about safe driving practices. Among the drivers, 156 (88.6%) never measured their blood glucose before, or during driving. The survey revealed that 86 (51.2%) of 168 patients had a history of at least one motor vehicle accident within the previous 5 years. The average road traffic accident rate per person/year was 0.21. Conclusions: The study revealed a lack of knowledge among drivers with diabetes treated with insulin or sulfonylureas concerning recommended safe practices for driving. This was associated with significant hypoglycemia while driving and an elevated rate of road traffic accidents.

Urban emission inventory optimisation using sensor data, an urban air quality model and inversion techniques

An optimisation scheme has been developed that applies a Bayesian inversion technique to a high resolution (street-level) atmospheric dispersion model to modify pollution emission rates based on sensor data. The scheme minimises a cost function using a non-negative least squares solver. For the required covariance matrices, assumptions are made regarding the magnitude of the uncertainties in source emissions and measurements and the correlation in uncertainties between different source emissions and different measurement sites. The scheme has been tested in an initial case study in Cambridge using monitored data from four reference monitors and 20 AQMesh sensor pods for the period 30 June 2016 to 30 September 2016. Hourly NOx concentrations from road sources modelled using ADMS-Urban and observed concentrations were processed using the optimisation scheme and the adjusted emissions were re-modelled. The optimisation scheme reduced average road emissions on average by 6.5% compared to the original estimates, changed the diurnal profile of emissions and improved model accuracy at four reference sites.

Optimal pavement management: Resilient roads in support of emergency response of cyclone affected coastal areas

Roads in poor road condition disrupt emergency operations in disaster-prone areas during emergency periods. Prolonged inundation of pavements from storm surge accelerates deterioration of pavements and increases maintenance cost. The objective of this study is to propose an optimized decision support system for pavement maintenance and rehabilitation (M&R) operations guided by geo-physical risk and community vulnerabilities. A case study of regional highways, arterial and collector roads at the district of Barguna, in Bangladesh is selected given the frequency of cyclones and storm surges in this area. A geo-physical risk and vulnerability (GEOPHRIV) index was estimated for each road’s segment by integrating the geo-physical risk; community, structure and infrastructure vulnerabilities; and damage indices. Linear programming was applied to optimize M&R strategies to ensure good pavement condition for all roads at a minimum M&R budget. Lifecycle optimization of M&R operations estimated that USD 2.49 million is the minimum annual budget that ensures having good average road’s condition in the study area. Most of the annual M&R budget will be invested for overlay and resealing treatments on the roads at high and medium GEOPHRIV areas. This study helps transportation authorities to identify deteriorated pavement sections, maintain the pavement periodically to prevent or minimize damage before storm surge, and allocate resources for M&R operations.