Master of Science / Department of Civil Engineering / Sunanda Dissanayake / In the United States, the mileage of unpaved roads is about 1.6 million miles. Total length of unpaved roads in Kansas is about 98,000 miles, of which about 78,000 miles are gravel roads. Most of the gravel roads are not posted with speed limit signs but regulated with a 55 mph blanket speed limit established by the Kansas Statutes. Surface conditions of gravel roads are very likely to change with time, space, and quality of maintenance work, making it even more necessary to have proper control of speeds on gravel roads. Normally used speed regulations and rules for freeways or other types of paved roadways might not be appropriate for gravel roads, especially for those local gravel roads which usually carry very low traffic in rural areas. Based on an extensive literature search, there was no specific rule or references to provide guidelines on how speed limits on gravel roads could be set. Therefore, an effort was made in this study to evaluate the effects of currently posted lower speed limits in some counties in Kansas, based on traffic characteristics and safety on gravel roads, with the intention of providing proper guidelines for setting speed limits on gravel roads in Kansas. In order to study traffic characteristics on gravel roads, field speed studies were conducted with automatic traffic counters on more than forty gravel road sections in seven counties in Kansas. Important speed measures, such as 85th-percentile speed and mean speed, were obtained from the raw data. A group of other related road characteristics were also recorded at the time of field data collection. Crash data on gravel roads were extracted from the Kansas Accident Recording System (KARS) database. Speed analysis on a number of gravel roads where the statutory imposed, unposted speed limit of 55 mph was utilized indicated that they are functioning at a reasonably acceptable level in terms of actual speeds. In order to evaluate whether there were differences in traffic speeds between two counties or groups which have different speed limit settings on gravel roads, t-test was used. The analysis found that there was no significant difference between the mean speeds in two counties, one of which has 35 mph posted speed limit on gravel roads while the other does not post any speed limits. Moreover, the mean speed on the sections with 35 mph posted speed was a little higher than that on gravel roads without any speed limits. Linear models to predict 85th-percentile speed and mean speed on gravel roads were developed based on speed data. Both models indicated that traffic speeds are not significantly affected by the speed limit, but are related with 90% confidence to road width, surface classification and percentage of large vehicles in traffic. Chi-square tests were conducted with the crash data, and the results indicated that the posted 35 mph speed limit on gravel roads had not resulted in either smaller total number of crashes or decreased proportion of severe crashes, compared to gravel roads where no speed limits were posted. Logistic regression models were also developed on four levels of crash severity, which indicated that gravel roads with higher speed limits are likely to experience higher probability of having injury crashes. Two mail-back surveys were also conducted to gather the opinions of county engineers and road users on the subject of suitable speed limits on gravel roads. The majority of county engineers believed that blanket speed limit should be used for gravel roads and does not need to be posted. Three restrictions: changeful road conditions, unpractical law enforcement, and limited funds, are basic reasons why they do not think that gravel roads should be posted. Besides that, a few respondents said 55 mph is too high for gravel roads and needs to be lowered. Majority of the road users suggested that all gravel roads be posted with lower speed limit signs. However, they were more concerned about law enforcement since they believe that posted speeds won't bring any benefits if no law enforcement patrol gravel roads. Based on all aspects looked into in this study, it does not appear that reducing the speed limits and posting it with signs, is going to improve either traffic operational or safety characteristics on gravel roads in Kansas, and therefore is not recommended for new situations.

The impact of transport and climate factors on dust formation and causation on gravel roads was analysed in this work. The condition of cover of gravel roads, when the dust spreading is minimized, was estimated. As well, the quality of gravel, used to upbuild the road cover, was assessed. It was suggested to regulate the reduction of dust on gravel covers by selecting certain sectors of gravel roads, choosing means to decrease the dustiness and determining the order of their usage, as well, as regulating the performance of technological process and control of the quality.

Šio darbo tikslas – kompleksiškai ištirti dulkėtumą ir triukšmą kaimo gyvenviečių žvyruotų kelių aplinkoje ir natūralių želdinių įtaką taršos lygiui. Atliktais tyrimais nustatyta, kad dulkių koncentracija kelyje su žvyro danga ir jo aplinkoje kelis kartus didesnė nei kelyje su asfalto danga ir iki 10 m atstumu nuo kelio viršijama leistinoji 0,5 mg m-³ koncentracijos vertė. Didžiausias dulkių sklaidos sulaikymas nustatytas pakelėje su liepų augmenija. Ištyrus dulkių dalelių kiekį pagal jų dydį (15 m atstumu nuo kelio krašto kur gyventojai dažniausiai būna lauke) nustatyta, kad pravažiavus pavienei transporto priemonei daugiausiai užfiksuota smulkiųjų (0,3-0,49 μm) dalelių - apie 45000 vnt. m-³. Ištyrus pavienės transporto priemonės sukeltą triukšmą nustatyta, kad asfalto ir žvyro dangų keliuose atviroje vietovėje 15 m atstumu nuo kelio garso lygis 6 dBA didesnis žvyruoto kelio atveju. Žvyro kelyje kai nėra kelkraštėje jokios natūralios atitvaros garso lygis 15 dBA didesnis nei kelyje su užtvara. Esant skirtingoms kelio kelkraštėje augmenijos užtvaroms, už jų triukšmo slopinimas skyrėsi apie 10 dBA, o efektyviausiai triukšmą slopina įvairių želdinių augmenija. / The main idea of this work - a comprehensive investigate dust and noise, gravel roads of rural settlements in the environment and natural greenery influence to the level of pollution. After finishing this research showed that concentrations of dust on the road with partition with a gravel surface and its atmosphere are several times higher than on the road with partition with asphalt and up to 10 m from the road exceeded the permissible 0.5 mg m-³ concentration value. The maximum delay dispersion of dust at the roadside with the lime trees. After research the amount of dust particles by size (15 m from the edge of the road where people is usually outdoor) found that the passing of single vehicle mostly recorded small (0.3 to 0.49 µm) particles - about 45,000 units. m-³. After research individual vehicle noise found that the asphalt and gravel roads in an open area of 15 m from the road sound level 6 dB above the gravel road. On gravel on the road with partition where there is no natural roadside partitions sound level 15 dB higher than the on the road with partition. At roadside vegetation in different road barricades for the noise attenuation of 10 dB difference, and the most effective noise levels of various plantation vegetation.

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En beräkningsmodell utvecklas för att skatta miljöpåverkan och ekonomiska effekter vid vägunderhållet grusning. Beräkningsmodellen används för att kunna jämföra alternativa metoder för grusning. Beräkningsmodellen testas genom ett testscenario med tre alternativa metoder för grusning. I alternativ ett används nytt grus och i alternativ två och tre används återvunnet grus. Studiens resultat visar att beräkningsmodellen kan användas för att skatta kostnad och miljöbelastning. Testscenariot visar att det är ekonomiskt och miljömässigt fördelaktigt att använda återvunnet grus vid grusning. Ur ett samhällsperspektiv är det viktigt att belysa fördelarna med att använda återvunnet grus, då detta kan motivera att fler faktiskt väljer detta alternativ och då brytning av naturgrus är en energikrävande process som påverkar miljön negativt. Studiens syfte är att skapa förståelse för miljömässiga och ekonomiska effekter vid återvinning av grus vid grusvägsunderhåll. För att uppnå syftet genomförs en fallstudie som besvarar frågeställningen hur miljömässiga och ekonomiska effekter kan skattas på grusvägsunderhåll. / A calculation model is developed to estimate the environmental impact and economic effects of gravel road maintenance. The purpose of the calculation model is to be able to compare alternative methods for graveling. The calculation model is tested through a test scenario with three alternative methods for graveling. In alternative one, new gravel is used and in alternatives two and three recycled gravel is used. The study's results show that the model calculation can be used to estimate cost and environmental impact. The test scenario shows that it is economically and environmentally advantageous to use recycled gravel in graveling. From a societal perspective, it is important to highlight the benefits of using recycled gravel, as this may motivate more people to actually choose this alternative. Because mining of natural gravel is an energy-intensive process that has a negative impact on the environment. The purpose of the study is to create an understanding of the environmental and economic effects of recycling of gravel during gravel road maintenance. To achieve this, a case study is conducted that answers the question how environmental and economic impacts can be estimated on gravel road maintenance.

There are around 300, 000 kilometer of gravel roads throughout the Swedish countryside, used every day by common people and companies. These roads face constant wear due to harsh weather as well as from heavy traffic, and thus, regular maintenance is required to keep up the road standard. A cost effective maintenance requires knowledge of where support is needed and such data is obtained through inventorying. Today, the road inventory is done primarily by hand using manual tools and requiring trained personel. With new tools, this work could be partially automated which could save on cost as well as open up for more complex analysis. This project aims to investigate the possibility of automating road inventory using computer vision and machine learning. Previous works within the field show promising results using deep convolutional networks to detect and classify road anomalies like potholes and cracks on paved roads. With their results in mind, we try to translate the solutions to also work on unpaved forest roads. During the project, we have collected our own dataset containing 3522 labelled images of gravel and forest roads. There are 203 instances of potholes, 614 bare roads and 3099 snow covered roads. These images were used to train an image segmentation model based on the YOLOv8 architecture for 30 epochs. Using transfer learning we took advantage of pretrained weights gained from training on the COCO dataset. The predicted road segmentation results were also used to estimate the width of the road, using the pinhole camera model and inverse projective geometry. The segmentation model reaches a AP50−95 = 0.746 for the road and 0.813 for the snow covered road. The model shows poor detection of potholes with AP50−95 = 0.048. Using the road segmentations to estimate the road width shows that the model can estimate road width with a mean average error of 0.24 m. The results from this project shows that there are already areas where machine learning could assist human operators with inventory work. Even difficult tasks, like estimating the road width of partially covered roads, can be solved with computer vision and machine learning.

Gravel roads are essential for economic development as they facilitate the movement of people, transportation of goods and services, and promote cultural and social development. They typically connect sparsely populated rural areas to urban centres, providing essential access for residents and entrepreneurs. Maintaining these roads to an acceptable level of service is crucial for the efficient and safe transportation of goods and services. However, substantial maintenance investmentis required, yet resources are limited. Gravel roads are prone to dust, potholes, corrugations, rutting and loose gravel. They deteriorate faster than paved roads, and their failure development is affected by traffic action and physical, geometric and climatic factors. Thus, more condition monitoring and proper road condition assessment are necessary for dynamic maintenance planning to reach efficiency and effectiveness using objective, data-driven condition assessment methods to ensure all-year-round access. However, objective data-driven methods (DDMs) are not frequently used for gravel road condition assessment, and where they have been applied, the practical implementation is limited. Instead, visual windshield assessment and manual methods are predominant. Visual assessments are unreliable and susceptible to human judgement errors, while manual methods are time-consuming and labour-intensive. Maintenance activities are predetermined despite dynamic maintenance needs, and the planning is based on historical failure data rather than the actual road condition. This thesis establishes a data-driven approach to gravel road maintenance describing the systematic assessment of the gravel road condition and collection of the condition data to ensure efficient and effective maintenance planning. This thesis uses a design research methodology based on a literature review, concept development, interview study and field experiments. A holistic approach is proposed for data-driven maintenance of gravel roads encompassing objective condition data collection, processing, analysing, and interpreting the findings for obtaining reliable information concerning the condition to gravel road decision support by utilising the opportunities presented by technological advancements, particularly sensor technology. Then, decision-making is primarily influenced by the objectively collected gravel road condition data rather than the evaluator’s perception or experience. The successful implementation of a data-driven approach depends on the quality of the collected data; therefore, data relevance and quality are emphasised in this thesis. The lack of data quality and relevance hinders effective data utilisation, leading to less precisionin decision-making and ineffective decisions. Furthermore, the thesis proposes a participatory data-driven approach for unpaved road condition monitoring, allowing road users to be part of the maintenance process and providing an efficient and effective alternative for collecting road condition data and accomplishing broad coverage at minimum cost. A top-down iiapproach for data-driven gravel road condition classification is proposed to achieve an objective assessment to address the lack of readily available quality and relevant condition data. The established data-driven approach to gravel road maintenance is evaluated and verified with field experiments on three gravel roads in Växjö municipality, Southern Sweden. The research findings indicate that properly implementing a data-driven approach to gravel road maintenance would ensure efficient and effective condition assessment and classification, which are a basis for a maintenance management system of gravel roads and enable road maintainers and authorities to achieve cost-effective decision-making. / Sustainable maintenance of gravel road

Approximately 75 percent (300 000 km) of the total Swedish road network and 20 percent(20 000 km) of the national road network consists of gravel roads. One of the most significantproblems associated with gravel roads is traffic-generated dust emission, which contributes tothe deterioration of the road surface and acts as a major source of particulate matter releasedinto the atmosphere, thereby involving public economics, road safety, human health, andenvironmental quality. In order to bind the fine granular material, which is prone to rise into theair, dust suppressants are applied on roads on a yearly basis. Methods for evaluating the efficiency of dust suppressants will facilitate in the selection of themost appropriate product and its optimal application rate. For example, methods forsupervision of residual dust suppressant concentration are valuable tools for estimatinglongevity and optimal application rates, and, consequently, effectiveness of different products. Application of the proper dust suppressant to a gravel road ensures road safety and ridingcomfort as well as creating a cleaner and healthier environment for residents in buildingsadjacent to the road. It also reduces the need and cost for vehicle repair, road maintenanceactivities, and aggregate supplementation. Both field-based and laboratory research were performed to evaluate the efficiency of varioussuppressants and the influence such factors as product concentration, leaching, and fine materialcontent have on the efficiency of different products. Within the field-based research, a newlydeveloped mobile methodology was used to measure dust emission on numerous test sectionstreated with various dust suppressants. In general, all dust suppressants tested, except apolysaccharide (sugar) and products, which form a brittle surface crust, i.e. lignosulphonate andbitumen emulsion, showed acceptable dust reduction. Test sections treated with a magnesium- or calcium chloride solution were the most effectivelydust suppressed. The application of solutions instead of a solid salts achieves a more uniformproduct distribution and, therefore, probably a more efficient performance. By applying acalcium- or magnesium chloride solution instead of traditionally used solids, the cost for annualdust control, as well as the environmental impact from the release of these chemicals in theenvironment, can be reduced by 50 percent. A significant problem when using dust suppressants is their tendency to leach during rainfalldue to their soluble properties. Residual chloride could be detected in the gravel wearing courseover a longer period of time than lignosulphonate and, therefore, showed more effective longtermperformance. Optimal percentages of fine material for minimal lignosulphonate andchloride leaching were found to be 15 percent by weight and 10-16 percent by weight,respectively. Ions of calcium chloride seemed to initiate flocculation of clay particles, therebypreventing them from leaching. Still, the fine material in gravel wearing courses has to be replenished regularly as indicated by studies of the longevity of fine material. Loss up to80 percent was found after two years. Toxicity tests show that dust suppressant application for dust control purposes, at traditionallyused application rates, does not constitute a threat to sensitive aquatic life. Tests on subsoilwater samples indicated elevated chloride levels, which possibly could cause corrosion to pipes,but not high enough to flavour drinking water. / QC20100616