Analytical Determination of Size and Location of Roadside Horizontal Sightline Offsets for Compound Curves

AASHTO’s guideline for geometric design of highways and similar guidelines require that roadside areas on the inside of horizontal curves be cleared of high objects to provide stopping sight distance. The guidelines have analytical models for determining the extent of clearance, known as the horizontal sightline offset or clearance offset, for simple curves. Researchers in the past have developed analytical models for clearance offsets for spiraled and reverse curves. Very few researchers developed analytical models for available sight distances for compound curves. Still missing are models for horizontal sightline offsets and locations of the offsets for compound curves. The objective of this paper is to present development of analytical models and charts for determining horizontal sightline offsets and their locations for compound curves. The paper considers curves whose component arcs are individually shorter than stopping sight distance. The resulting models and the charts have been verified with accurate values determined using graphical methods. The models and the charts will find application in geometric design of highway compound curves.

Automatic Lane-Level Intersection Map Generation using Low-Channel Roadside LiDAR

A lane-level intersection map is a cornerstone in high-definition(HD) traffic network maps for autonomous driving and high-precision intelligent transportation systems applications such as traffic management and control, and traffic accident evaluation and prevention. Mapping an HD intersection is time-consuming, labor-intensive, and expensive with conventional methods. In this paper, we used a low-channel roadside light detection and range sensor(LiDAR) to automatically and dynamically generate a lane-level intersection, including the signal phases, geometry, layout, and lane directions. First, a mathematical model was proposed to describe the topology and detail of a lane-level intersection. Second, continuous and discontinuous traffic object trajectories were extracted to identify the signal phases and times. Third, the layout, geometry, and lane direction were identified using the convex hull detection algorithm for trajectories. Fourth, a sliding window algorithm was presented to detect the lane marking and extract the lane, and the virtual lane connecting the inbound and outbound of the intersection were generated using the vehicle trajectories within the intersection and considering the traffic rules. In the field experiment, the mean absolute estimation error is 2 s for signal phase and time identification. The lane marking identification Precision and Recall are96% and 94.12%, respectively. Compared with the satellite-based,MMS-based, and crowdsourcing-based lane mapping methods,the average lane location deviation is 0.2 m and the update period is less than one hour by the proposed method with low-channel roadside LiDAR.

Reducing congestion and emissions via roadside unit deployment under mixed traffic flow

It is expected that for a long time the future road trafc will be composed of both regular vehicles(RVs)and connected autonomous vehicles(CAVs).As a vehicle-to-infrastructure technology dedicated to facilitating CAV under the mixed trafc fow,roadside units(RSUs)can also improve the quality of information received by CAVs,thereby infuencing the routing behavior of CAV users.This paper explores the possibility of leveraging the RSU deployment to afect the route choices of both CAVs and RVs and the adoption rate of CAVs so as to reduce the network congestion and emissions.To this end,we frst establish a logit-based stochastic user equilibrium model to capture drivers’route choice and vehicle type choice behaviors provided the RSU deployment plan is given.Particularly,CAV users’perception error can be reduced by higher CAV penetration and denser RSUs deployed on the road due to the improved information quality.With the established equilibrium model,the RSU deployment problem is then formulated as a mathematical program with equilibrium constraints.An active-set algorithm is presented to solve the deployment problem efciently.Numerical results suggest that an optimal RSU deployment plan can efectively drive the system towards one with lower network delay and emissions.

Assessing the Influence of Roadside Advertising on Traffic Distraction and Its Interplay with Inside Vehicle Distractions: A Cross-Cultural Study in Jordan and Kuwait

Limited research has explored roadside advertisements’ effects on road user behavior in Middle Eastern countries. This study aims to understand distraction perceptions, including advertisements, their impact on behavior, and potential influences from advertisement type, in-vehicle distraction, and country factors (reflecting culture and environment). A standardized questionnaire was administered in Jordan and Kuwait, complemented by observations across three segment types: roadside advertisements, commercial signs, and road signs as control segments. Descriptive and inferential statistics were used. Results indicated a significant disparity in distraction perception between the two groups. Advertisement presence influenced Kuwaiti but not Jordanian behavior. Behavior varied by advertisement type in Jordan, not Kuwait, and in-vehicle distraction did not impact driver behavior. The study suggests explicitly revising advertising policies with a traffic safety focus. Overall, the study contributes insights into road user perceptions and behaviors, highlighting the complex interplay of distractions and advertising on road safety. Further research is required to validate these findings and shape road safety regulations.

Quantification of Above-Ground Biomass and Carbon Sequestration Potential of Roadside Trees in the Plateau Department of Benin Republic

Roadside trees are effective natural solutions for mitigating climate change. Despite the usefulness of trees to carbon sequestration, there is a dearth of information on the estimation of biomass and carbon stock for roadside trees in the study area. This study aimed to estimate the carbon stock and carbon dioxide equivalent of roadside trees. A complete enumeration of trees was carried out in Kétou, Pobè and Sakété within the communes of the Plateau Department, Bénin Republic. Total height and diameter at breast height were measured from trees along the roads while individual wood density value was obtained from wood density database. The allometric method of biomass estimation was adopted for the research. The results showed that the total estimations for above-ground biomass, carbon stock and carbon equivalent from all the enumerated roadside trees were 154.53 mt, 72.63 mt and 266.55 mt, respectively. The results imply that the roadside trees contain a substantial amount of carbon stock that can contribute to climate change mitigation through carbon sequestration.

Heavy metal concentrations in plants and soils at roadside locations and parks of urban Guangzhou

Levels ofCu, Ni, Zn, Pb and Cr were measured in soils and trees in urban Guangzhou, China. Tree and soil samples were collected from the roadside, urban parks and a university campus. Mean concentrations of Cu, Ni, Zn, Pb and Cr in tree leaves were 28.3, 7.7, 142.1, 23.4, and 195.1 mg/kg respectively. In a comparison of heavy metal concentrations in tree leaves between roads and park locations, only Pb concentrations were significantly higher in the former. Heavy metal concentrations were lower in the roots compared to leaves. It indicated that heavy metal pollution of trees is mainly from air pollution, For all top soil samples the mean concentrations of Cu, Ni, Zn, Pb and Cr were 24.3, 17.3, 121.5, 63.9 and 88.7 mg/kg, respectively. Heavy metal concentrations in roadside soils were higher and their coefficient of variation was higher than those in urban parks. Comparing heavy metal concentrations in trees and soil between urban Guangzhou and Hainan Island, China, Cu, Ni, Zn, Pb and Cr levels in soils and plants in urban Guangzhou were evidently affected by the human impact. However the heavy metal content in the soil compared to some international standards do not give cause for concern. Some observations on the implications of the data for environmental monitoring are made.

Lead Concentration in Hong Kong Roadside Dust after Reduction of Lead Level in Petrol

Samples of roadside dust were collected from 30 sites in Hong Kong.The total concentrations of 10 metals in the samples were analyzed,and the correlation coefficients among the metal contents and the annual average daily traffic(AADT)in 1986 were determined.Pb was found to have a significant correlation(P<0.01)with AADT.No correlation was found between Al, Ba,Cd,Cr,Cu,Fe,Mn,Ni,and Zn with respect to AADT.A general decrease in the level of Pb in roadside dust in the past few years has been observed since the reduction in the level of lead in petrol.1989 Academic Press,Inc.

Assessment of Heavy Metals, pH, Organic Matter and Organic Carbon in Roadside Soils in Makurdi Metropolis, Benue State, Nigeria

Roadside soil samples were collected from four sites (heavy traffic area (Wurukum);industrial site (Gboko road);residential area (Federal Lowcost) and FederalMedicalCenter(Wadata) representing different activities across the Benue Metropolis. At each of the sample site, roadside soils were collected at different distance from the edge of the main road (2, 10, 30, 40 and 60 meters). In each of the distance, roadside soil were collected at three depth of 0 -1 cm, 2 -4 cmand 4 - 6 cm for the determination of pH, organic matter, organic carbon, Cu, Cd, Fe, Pb, As, Mn, Zn, Cd and Ni. pH, electrical conductivity (EC), organic matter and organic carbon were determined using standard procedures, while heavy metals were determined using Perkin-Elmer Analyst 300 Atomic Absorption spectroscopy (AAS). Zinc was observed to show the higher levels in all the sampling sites, such higher level can be related back to the wear-and-tear of vehicle components as a result of the stop-start traffic patterns and brake pads. The concentrations of all the metals in the four sampling sites decreased exponentially with distance from the edge of the road and dropped to the minimum levels at about 60 meters. Similarly, mean concentrations of Cu, Fe, Pb, As, Mn, Zn, Cd and Ni were significantly higher around the industrial area (Gboko road) and heavy traffic (Wurunkum) areas than other sampling areas followed an increasing trend with the increase in depth. The vertical movement of all the metals, exhibited predominant association with soil pH and organic carbon. From the results of this study, the pH of the roadside soils from all the sampling points ranged from 4.56 to 7.71, which enhances increased of heavy metals down the soil profiles. Organic carbon content ranged of 0.27% to 5.44% across all the sampling points appears to increase the mobility of all the metals to a depth6 cm. The values of the heavy metals suggest that automobiles and traffic activities are a major source of these metals in the roadside soil within the study area. Also, with the exception of Pb, Fe and Cd, the levels of Cu, As, Mn, Zn and Ni in the present study were lower as compared with results found by other researcher in various countries worldwide.

Construction Features of Small Roadside Parks in Tropical Area——A Case Study of Zhanjiang City

Accessibility and flexibility of small roadside parks make them significant transitional spaces in urban landscape environment. Three representative small parks in Zhanjiang City, a typical tropical city in south China, were selected to analyze their location features, spatial processing, demonstration of regional landscapes and recreational characteristics. It was proposed that construction of small roadside parks in tropical area should put human needs on the priority, present regional features of tropical garden landscapes, and focus on inheritance and innovation of regional cultures.

New Spiral Curves for Appropriate Transition of Minimum Roadside Clearance on Simple Curves

Guidelines for geometric design of highways require that the inside of horizontal curves be cleared of obstructions to sight in order to provide necessary sight distance. Many of these guidelines use one analytical model for determining minimum clearance offsets. These offsets are suitable for middle sections of long curves because the analytical model was derived with consideration that drivers on the curves are able to see downstream curved sections whose lengths are equal to stopping sight distance. Applying these offsets to straight sections near beginnings and ends of the curves results in unnecessary clearance costs since sightlines are accommodated within lanes and wide shoulders. This paper presents a new analytical model for gradual transition of clearance from zero on straight sections to the minimum value required at the middle of horizontal curves. The model is based on new spiral curves whose mathematical equations incorporate driver location, object location, radius of horizontal curve, length of horizontal curve, and design sight distance. Moreover, the already known Euler’s spiral curve is examined whether or not it is also suitable for transitioning clearance. It is found that the Euler’s spiral consistently underestimates clearance offsets. Underestimation of the offsets is due to high degree of sharpness of the Euler’s spiral which renders the spiral unsuitable for transitioning clearance. Finally, the analytical model is presented in the form of a design chart. Without compromising safety and mobility of highways, use of either the design chart or the analytical equations will help agencies save money that would otherwise be spent for unnecessary extra clearance of roadside areas near beginnings and ends of horizontal curves.

Examining the effect of speed, roadside features, and roadway geometry on crash experience along a rural corridor

This paper presents a current investigation into crash experience along a 15.7-mile rural corridor in southwest Montana with the aim of better understanding crash causal factors along the corridor. The study utilized ten years of crash data, geometric data, and observed freeflow speed data along the corridor. A systematic approach was used where every tenth of a mile was described in term of the crash experience, speed, alignment, and roadside features. Using bivariate and multivariate statistical anal-yses, the study investigated the crash experience along the corridor as well as some of the underlying relationships which could explain some of the crash causal factors. Results show a strong association between crash rates and horizontal curvatures even for flat curves that can be negotiated at speeds above the posted speed limit, per the highway design equations. Higher crash rates were also found to be associated with the difference between the observed free-flow speeds and the speed dictated by the curve radius or sight distance as per the design equations. Further, results strongly support the safety benefits of guardrails as evidenced by the lower crash rates and severities. The presence of fixed objects and the steepness of side slopes were also found to have an effect on crash rates and severities.

Suitability of the Euler’s Spiral for Roadside Clearance in Order to Provide Stopping Sight Distances

The AASHTO’s guideline for geometric design, also known as the green book, requires that the inside of horizontal curves be cleared of obstructions to sight lines in order to provide sufficient sight distances. Recently, innovative use of Euler’s spiral for determination of clearance offsets has been proposed. However, suitability of the offsets as minimum criteria has not been evaluated. This paper presents comparison between the proposed offsets and minimum offsets determined with the computational method suggested in the green book. Results of comparison show that offsets determined with innovative use of the Euler’s spiral are always longer than minimum values determined with the computational method. The differences in lengths of the two sets of offsets increase with decrease in curve radii. Therefore, on sites with large radii offsets determined through innovative use of the Euler’s spiral may be implemented in the field since the offsets are only slightly longer than minimum offsets. On sites with short radii some offsets on tangent sections are very long such that they result in extra cleared areas that will not accommodate sightlines. The areas that do not accommodate sightlines may result in unnecessary extra earthwork costs where highways are located in cut zones. Additionally, it has been suggested in this paper that designers also consider other curves, including elliptical arcs, for roadside clearance envelopes. One advantage of elliptical arcs is that they are flexible to align with boundaries of clear zones on tangent sections regardless of sizes of radii of horizontal curves. Besides, most offsets to elliptical arcs are comparable to those determined with the green book’s computation method. An example of design chart has been presented for practitioners to use. The chart is for minimum offsets needed to provide a given sight distance while gradually transitioning clearance from boundaries of clear zones on tangent sections.

An Innovative Approach to Mitigate Vehicular Emission through Roadside Greeneries: A Case Study on Arterial Roads of Dhaka City

With the surge of human population, the need for transportation of goods and people also concomitantly increases, resulting in urban air pollution through emission from motorized traffic especially in developing countries. The extent of environmental pollution in an urban setting is significantly influenced by the pollutants of vehicular fuel combustion. Many effective measures are required in cities to sequester carbon thereby helping to reduce automobile pollution. Roadside greeneries can serve as ecological elements which reduce the concentration of pollutants from vehicular emissions by their direct involvement in absorbing vehicular emitted carbon. In this context, in this study an attempt has been taken to assess contribution of roadside greeneries in absorbing vehicular carbon dioxide emission. A case study has been conducted on arterial roads of mega city Dhaka to quantify the vehicular carbon emission and correlate it with roadside trees to absorb the emitted carbon dioxide. It is noted that in Dhaka city, carbon dioxide is accounted for more than ninety percent of air pollution. To achieve our goals, two busiest arterial roads (namely Mirpur Road and Rokeya Shoroni Road) were taken into account to quantify vehicular carbon emission as well as assess carbon absorption by roadside greeneries. Carbon absorption by different sizes of trees has been quantified using the amount of woody biomass. In addition, absorption by grass-shrubs-herbs has been quantified by the area they cover. The results thus obtained show that indeed the road with more side greeneries absorbs more vehicular emitted carbon dioxide. It is therefore evident that plantation of more roadside trees is an effective measure of reducing air pollution and consequently turning a city to become healthier and more suitable for living.

Minimum Roadside Clearance Offsets on the Inside of Reverse Curves Based on Flat Spirals

Design guidelines require that high objects on the inside of horizontal curves be cleared so as to provide sufficient sight distance. An example of the guidelines that require such clearance is the AASHTO’s Green Book. The Green Book has an analytical model for determining minimum clearance for a given design sight distance. The model is well suited for middle sections of long curves. Applying such clearance to sections near beginnings and ends of the curves and to sections where there is reverse of curvature will result in over-clearance. Over-clearance implies extra cost of earthwork where highways pass in cut zones. To avoid such extra costs the guideline suggests using the graphical method to determine exact clearance offsets. The graphical method is accurate but it is also tedious and time consuming. This study developed analytical models for efficiently determining clearance offsets that match the offsets determined with the graphical method. The offsets are ordinates from driver paths to flat roadside spirals that make the boundary of the roadside area to clear. Mathematical equations for the spirals comprise of terms related to highway speed (in the form of design sight distance), curve features, and driver locations. In turn, these terms define magnitudes of the offsets to the spirals. Combination of the terms results in many parameters to the extent of making difficult development of design charts for offsets. However, examining suitability of published offset charts for simple curves as estimates of offsets for sites with reverse curves leads to finding that the charts are suitable as long as the reverse curves have common tangents that are at least as long as 25% of design sight distance. For reverse curves with no common tangents, offset charts have been developed and presented in this paper. Practitioners can use these charts or the derived equations to determine clearance offsets for new sites as well as for existing sites that are deficient in design sight distance.

The Safe Navigation of Partial Motion Planning Based on “Cooperation” with Roadside Fixed Sensors in VANET

In recent years, many methods of safe vehicle navigation and partial motion planning (PMP) have been proposed in vehicular ad-hoc network (VANET) field. In order to improve the limitation of traditional PMP, this paper presents a novel effective way to plan motion with cooperation of roadside fixed sensors (RFSs). With their cooperation, the vehicles can get the surrounding information quickly and effectively, and give highly accurate projections about the near future conditions on road. After proposing our algorithm, the worst case is analyzed and methods are found to solve the problem. Finally we conduct one elemental contrast experiment, driver situation awareness, with or without the “cooperation” of RFSs in highway scenarios. The result shows that the vehicles can make a better PMP based on the forward conditions received from RFSs, and extend the warning distance obviously when emergency happens.

Development and application of photocatalytic coating for roadside NO_(x) mitigation in Hong Kong

A facile chemical method for the development of photocatalytic coating products was proposed based on practical application perspective for the Hong Kong roadside nitrogen oxides(NO_(x))mitigation.TiO_(2)-based photocatalytic coating PC-C film with crystallized size of around 5–6 nm was synthesized with the peptization of H_(2)O_(2).The PC-C coating possesses a super-hydrophilicity surface and is proven to have a NO_(x)degradation rate of 46.8%with an optimum pH level of 7.In addition,the PC-C coating presents a promising photocatalytic NO_(x)degradation compared with other commercially available coating products and P25 when applied on two building materials of poly-methyl methacrylate(PMMA)and concrete surface.A weather resistance simulation and a 180-day on-site field trial were carried out the attenuation effects of photocatalytic coating applied in outdoor exposure.Based on epidemiological estimation and field investigation,hospital admissions for respiratory diseases(HARD)and mortality cases(MC)could be reduced with the application of PC-C coating along the street canyon.This work demonstrates the feasibility of air pollution control measures for the local roadside NO_(x)using photocatalytic technology,offering promising health benefits with environmental remediation.

SEASONAL AND DIURNAL VARIATIONS OF PM_(1.0),PM_(2.5) AND PM_(10) IN THE ROADSIDE ENVIRONMENT OF HONG KONG

PM1.0 （fine particles, with diameter 〈 1 pm）, PM2.5 （fine particles, with diameter 〈 2.5μm） and PM10 （coarse particles, with diameter 〈 10 μm） were measured at 24-hour intervals near a high-traffic road in Hong Kong, from October 2004 to September 2005. Mass concentrations were determined for the three particle fractions, averaging for PM1.0, PM2.5 and PM10, respectively, 44.5±18.4, 55.4±25.5 and 81.3±37.7μg·m^-3, PM2.5 was 3.7 times the U.S. EPA＇s annual NAAQS of 15 μg·m^-3,. Overall, PM1.0 accounted for 44 to 69% （average 57%） of PM10, while PM2.5 accounted for 58 to 82% （average 71%） in this study. The particulate masses showed obvious seasonal patterns with high concentrations in cold seasons and low in warm seasons, especially high concentrations of PM2.5-10 during the cold seasons. Diurnal variations of mass concentrations of PM2.5 were determined during July, showing two major peaks in the morning and afternoon rush hours.

Heavy metals accumulation in suburban roadside plants of a tropical area(Jengka,Malaysia)

Introduction:This study aims to examine the uptake and translocation of Cd,Cu,Fe,and Pb in different parts of three roadside plant species grown in the semi-urban of Jengka,Pahang,Malaysia.Methods:Heavy metal concentrations were determined from various parts of Athyrium esculentum(AE),Chromolaena odorata(CO),and Lantana camara(LC).The bioconcentration factor(BCF)and translocation ratio of heavy metals from soils to plants were estimated.Results:Fe showed the highest metal concentration determined(<850 mg kg^(−1)),while Cd showed the lowest metal concentration observed(<0.12 mg kg^(−1))in all plants.Heavy metal concentration in the roadside plants was higher than metal determined in the same species from an uncontaminated site.Principal component analysis(PCA)suggests anthropogenic and natural sources of heavy metal.Plant roots slightly enriched by Cd and Pb(BCF<1),while the leaves absorbed and accumulated Cu and Fe(BCF>1).The translocation ratio of four metals suggests that absorption of the three plants had the rank:root>stem>leaves.Conclusion:The metals in the root zone transported weakly to the stem but more strongly mobilized to leaves when available in the stems.A comprehensive study of heavy metal concentration in a variety of roadside plants in the tropical area should be done in the future ensuring the precise source and translocation mechanisms.

Concentrations of anthropogenic Pt and Pd in urban roadside soils in Xuzhou,China

The potential accumulation of platinum group elements(PGE)in the environment from automobile catalysts is high in urban areas,with the major sinks being roadside soils.Therefore,this investigation presented the detailed study on characterized concentrations of Pt and Pd and their enrichment ratios in urban roadside soils in Xuzhou,China in March 2003.Data from 21 roadside topsoil samples analyzed by inductively coupled plasmamass spectrometer(ICP-MS)illustrated that the medians of concentrations of Pt and Pd were 2.9 and 2.8 ng/g,respectively.Hierarchical clustering analysis indicated that Pt and Pd were mainly from traffic emissions.Compared to unpolluted soils,computation of Pt and Pd enrichment ratios suggested that the Xuzhou roadside soils had average enrichment factors of 3.53 for Pt(in range of 1.22–5.73)and of 3.37 for Pd(in range of 1.35–4.46).Lower Pt/Pd ratios(in range of 0.35–2.86)in relation to similar studies in other countries were observed,which might be due to the different Pt/Pd ratios in Chinese automobile catalytic converters.Moreover,fine fraction(,250 mm)contained higher concentrations of Pt and Pd compared to the coarse fraction(250–500 mm).

Innovative roadside design curve of lateral clearance： Roadway reverse horizontal curves

This paper presents a proposed concept of a spiraled roadside curve for determining the required lateral clearance that satisfies sight distance needs on a roadway reverse hori- zontal curve. The spiraled roadside curve was evaluated in the context of roadway plan view. The characteristics of its corresponding lateral offsets were analyzed. It was found that the ratio of the radii for the two reversing circular curves was the major factor that impacted the ratio of the required offset to the maximum offset of a circular curve. A single design chart and a design table were developed. The required offsets at alignment reversing sections were far less than those recommended by the American Association of State Highways and Transportation Officials （AASHTO） and those required at the approach and departure sections of a roadway simple curve. At the common point of the two reversing circular curves having a radius ratio R2/R1 ranging from 0.5 to 2, the required offsets were approximately 34%-66% of the maximum offsets recommended by AASHTO and approximately 41%-79% of those required in the case of a simple curve. The engi- neering implications of the proposed spiraled roadside curve are multifold： （a） it can be designed in a way similar to traditional roadway design, （b） it avoided the application of numerous design charts and extensive computations, （c） it can be easily staked on the field, （d） it not only greatly improved the A_ASHTO approximate approach, but also improved roadway design consistency.