PURPOSES : The purpose of this study was to investigate the performance of additives that affect internal curing in order to reduce the damage occurring in concrete pavements.
METHODS : SAP was used as an additive to reduce internal curing in concrete pavements. SAP is an additive that has a very high absorption rate which prevents concrete wrappers from externally draining water. To evaluate the internal curing performance according to the ratio of SAP, we identified the number of cracks and amount of abrasion reduction.
RESULTS : Plastic shrinkage and durability of a concrete mixture with added SAP were evaluated. The following results were obtained: (1) SAP showed a tendency to reduce slumps due to absorption of the concrete mixture. (2) It was possible to verify that concrete condensation did not occur during the penetration resistance test and that the initial curing did not lead to reactions within the mixture. (3) Adding more than 0.6% of SAP for dry curing resulted in greater compressive strength at all ages than OPC, with the highest compression strength of 0.9% after 56 days. (4) Regarding abrasion resistance, it was found that adding SAP was 30~50% better than adding the OPC mixture, and at 0.9% compression strength, abrasion resistance showed the best performance. (5) In the chlorine ion immersion resistance experiment, the passing charge of the OPC mixture was rated “high,” but it was rated “normal” in SAP. The results showed that the addition of SAP improved the water density of concrete due to internal curing effects, and that it showed the greatest chlorine ion penetration resistance for a compressive strength of 0.9%. (6) Regarding plastic shrinkage resistance, cracks did not occur on the surface until the end of the experiment, but the plastic shrinkage rate upon addition of SAP was relatively low compared to that of the OPC mixture.
CONCLUSIONS : Recent studies have shown that internal curing techniques can be applied using SAP to prevent shrinkage due to the loss of water and to decrease the effects of hydration. If internal curing effects are expressed using SAP, it is thought that contraction due to a loss of moisture and reduction in sign language reaction can be prevented.
PURPOSES : The retroreflectivity of pavement markings for road safety was evaluated.
METHODS : Field tests of pavement markings, which are characters, symbols, crosswalks, and stop lines, but do not include line markings, were conducted using a portable retroreflectometer with the purpose of evaluating the retroreflectivity according to the type of pavement markings and roads. Furthermore, changes in retroreflectivity due to wheel passing and wet conditions were evaluated. Here, 192 test points for evaluating the retroreflectivity of pavement markings, 5 test points for evaluating reductions in retroreflectivity during conditions of wetness, and 28 test points for checking variability due to type of testing device were selected on major and minor arterial roads in Seoul.
RESULTS : The average retroreflectivity of pavement markings measured in this study was 115.7 (mcd/m2·lux), which is lower than the minimum retroreflectivity required six months after installation but higher than the minimum remarking retroreflectivity required by Seoul city. The retroreflectivity of pavement markings measured on minor arterial roads was 69.1% of that on major arterial roads. The average retroreflectivity of pavement markings was reduced to 43.1% by wheel passing, which is below the remarking criterion. The average retroreflectivity measured on wet pavement markings was 43.7 (mcd/m2·lux), which is a ninth of that under dry conditions. The test results showed that retroreflectivity in the rain was much lower than the required value in the case of rain, which is 175 mcd/m2·lux, as issued by Seoul city. Compared with mobile retroreflectometers, a portable retroreflectometer produced 17% higher retroreflectivity based on the results of 28 test points.
CONCLUSIONS : Based on the field tests, the retroreflectivity of pavement markings, i.e., characters, symbols, crosswalks, and stop lines, was higher than the average remarking criterion. However, the retroreflectivities of pavement markings passed by the wheel or in rain were lower than the remarking criteria. Considering that the remarking criteria in Seoul city are higher than those in Europe and the test results in this study indicate much lower values than those required in Seoul, further study is necessary to be able to properly modify the criteria for retroreflectivity.
PURPOSES : The driver's ability to make a commitment has resulted in excessive force and a lack of commitment. To solve this problem, we are developing an algorithm that analyzes resolution in real-time by introducing IoT and informs drivers of the completion of compaction. METHODS : Real-time compaction was analyzed by installing accelerometers on the rollers. To evaluate the algorithms, we conducted an apparent density test.
RESULTS : The algorithm data and apparent density test data showed similar trends. This means that the proposed algorithms are sufficiently reliable. However, a lack of data samples and the fact that only data prior to completion of the commitment were analyzed may indicate a lack of reliability.
CONCLUSIONS : In subsequent studies, the number of samples will be increased and the data after completion of the commitment analyzed to increase reliability. Introducing a tachometer will prevent the TVL from falling sharply when the direction of the rollers' progress changes. In addition, it is also planned to upgrade the algorithms by researching cases in which the algorithms did not produce satisfactory results owing to problems such as temperature and speed.
PURPOSES : This study was conducted to evaluate the performance of pressure relief joints (PRJs) installed on highways for preventing blow-ups.
METHODS : To evaluate the performance of a PRJ, pavement surface images were acquired by conducting a follow-up survey through on-site visual inspection and an automated pavement condition survey. The PRJ widths in the acquired pavement images were measured using image analysis software, and major distress in the PRJ was identified. The relationship between the performance period and the joint width was bi-linearized, and the causes of distress and repair methods for PRJ were suggested.
RESULTS : As a result of the first survey, it became known that the width of a PRJ rapidly decreases after installation owing to an expansion of the concrete slab. The width of a PRJ continued to decrease, with 94% of the joint below 30 mm and 64% of the joint being below 10 mm, based on the fourth survey. The PRJ width of an Alkali-Aggregate Reaction (AAR) section decreased more than that of a normal section, but the difference in the average width between both sections decreased from 9.7 mm to 2.7 mm over the measured period. A bilinear estimation equation was developed based on the survey data. Through the estimation equation, it could be confirmed that joint contraction accelerated after installation owing to the effects of AAR, and that the joint widths of both sections converged to a similar level over the measurement period. As the result of the major distress analysis indicates, joint seal failure occurred in 70% of the joints, and the distress rates in terms of cracks, edge breakouts and spalling, and patching were 73%, 57%, and 28%, respectively.
CONCLUSIONS : With the follow-up survey it could be confirmed that the concrete slab continued to expand despite seasonal changes, maintenance of the PRJ, and additional installation of new PRJs. The expansion of the concrete slab due to AAR is considered to be closely related to PRJ behavior. In addition, it is judged that major distress of the PRJ occurs at an early age owing to the instantaneous release of excessive compressive stress inherent in the slab during joint cutting.
PURPOSES : The purpose of this study was to identify the availability of Grip-Tester, which can be used as continuous friction testers, for estimating the skid resistance of pavements by examining its basic performance.
METHODS : Based on a literature review, various factors influencing skid resistance on road surfaces were described, and the subject to be evaluated were proposed. Friction tests were conducted at various operating speeds to assess the water supply performance, repeatability, and reproducibility of the measurement results. Both the British pendulum number (BPN) and mean texture depth (MTD) were examined to confirm the relationship between the Grip Number(GN) and surface texture.
RESULTS : The results of the watering test indicate that more than 91% of valid measurements can be obtained at the maximum operating speed of 90 km/h to maintain a water film thickness of 0.25 mm. The repeatability and reproducibility of the measured GN were derived from the cross-correlation analyses to be 90.9% and 87.4%, respectively. It was found that the variations in GN values according to operating speeds follow an exponential model similar to the commonly known Penn State model, which can be considered to be due to the effect of texture on skid resistance.
CONCLUSIONS : The grip tester is suitable for continuously surveying the skid resistance because GN datasets are reliable at variable operating speeds and correlate with the surface texture. This method may provide objective data for making decisions regarding the maintenance of skid resistance through periodic full-scale investigations with the tester in the future.
PURPOSES : The purpose of this study was to evaluate the newly developed Guss mastic asphalt mixtures, called EQ-mastic asphalt mixtures, which contain melted additives for decreasing cooking time.
METHODS : A series of experiments were performed to investigate the effectiveness of the melted additives in EQ-mastic asphalt mixtures. Both the existing Guss mastic asphalt mixture and the EQ-mastic asphalt mixture were produced with the same amounts of asphalt binders, aggregates, and fillers, but the existing Guss mastic asphalt mixture contained 3% Trinidad lake asphalt (TLA). The EQ-mastic asphalt mixture contained 3% of additives, including TLA and polyolefin. The physical material performances of both mastic asphalt mixtures were obtained by conducting the Luer fluidity test, penetration test, dynamic stability test, and low-temperature bending test. The results of the tests for the existing Guss mastic and EQ-mastic asphalt mixtures were compared.
RESULTS : The fluidity, penetration, dynamic stability, and low-temperature bending strains of both the existing Guss mastic and EQmastic asphalt mixtures all satisfied the standard values provided in the production and construction guides of the Guss mastic asphalt pavement.
CONCLUSIONS : When melted additives containing polyolefin are used in the production of Guss mastic asphalt mixtures, the cooking time decreases, so that the corresponding energy consumption and asphalt fume amount can be reduced. Therefore, an EQ-mastic asphalt mixture is proposed for use as an eco-friendly pavement material.
PURPOSES : The purpose of this study is to establish design criteria for right-turning lanes by analyzing the relationship between the speed and geometry of right-turning lanes in urban areas. METHODS : A right-turn vehicle with a traffic island was surveyed for 32 geometries and 4,012 vehicles. Using multiple regression, we developed a running speed prediction model based on the running speed characteristics and geometry scale.
RESULTS : According to the analysis of the running speed of the right-turning channel, the 85th speed was 34.5-38.3 km/h, depending on the right-turning lane radius, and 32.4-39.0 km/h, depending on the channel width group. Based on the multi-regression, the right-turning radius and the channel width variables were statistically significant because of the influencing factors of the road speed. Two independent variables were positive (+) coefficients.
CONCLUSIONS : In this study, we investigated the running speed state on the right-turning channel and the factors that influenced the running speed. In addition, the relationship between the running speed and other factors was modeled through statistical analysis, and a running speed prediction model was established. It was observed that the driving speed increased as the geometry scale increased. Based on the derived running speed model, the maximum design criteria for limiting the speed of the conductive channelized right-turning lane in urban areas were established.
PURPOSES : In this study, the installation standards for micro-roundabouts at the intersection of local streets with two entering lanes of a 3.0 m lane width were developed.
METHODS : The inscribed circle diameter where a design standard vehicle could turn around safely based on the lane width and speed was analyzed using AutoTURN software. A total of 864 analysis scenarios for different entering volume and left-turning ratio (10%, 20%, 30%, and 40%), intersection type (three-way and four-way), heavy vehicle ratio (0%, 5%, and 10%), and circle lane turning speed (10, 15, and 20 km/h) conditions were established and evaluated. VISSIM Micro-Simulation was used to estimate the entering volume for microroundabouts with LOS C. RESULTS : The results showed that the estimated entering volumes of the three-way and four-way micro-roundabouts with LOS C were 300~400 and 200~400 vehicle/hour/lane, respectively. CONCLUSIONS : It is demonstrated that the standard volume of entering vehicles for micro-roundabouts is approximately 200 vehicle/ hour/lane, considering the number of approach lanes, designed speed of circulating lanes, left turn ratio, and heavy vehicle ratio.
PURPOSES : Many people recommend the expansion of the drone market and various ways of using drones. However, unreasonable expansion may cause various social problems. Therefore, criteria and systems for the expansion are required. This paper presents a review of the system using drones for managing and enforcing illegal parking, and recommendations on improvement. METHODS : This paper presents a review of the system using drones for managing and enforcing illegal parking, and recommendations on improvement.
RESULTS : This study shows that new enforcement criteria are required for a new enforcement method using drones. In addition, consignment operation is needed to solve workforce shortage and secure expertise, and flight mitigation criteria are required, considering the illegal parking characteristics based on region and time. Finally, CCTV operation guidelines should be improved to clarify the definition of drone images and prevent unreasonable information collection. CONCLUSIONS : Illegal parking enforcement using drones is an efficient method that is highly feasible and solves enforcement limitation issues, such as the lack of workforce and equipment. A prior institutional review is required to apply new technologies more efficiently, and proposals on improving the legal systems with limitations are required through continuous research.
PURPOSES : The aim of this study is to develop equitable smart mobility indicators for road infrastructure users based on the recognition of lack of social equity evaluation indicators from the perspective of road infrastructure users.
METHODS : In this study, vertical equity was expressed as the ratio of tolls to users' willingness to pay, depending on the income level. In each area, the time of travels to frequent destinations may differ, depending on the road infrastructure configuration use of tolled and untolled roads. When using tolled roads to save travel time, users have to pay tolls. In this case, the number of tolls that users have to pay and the users’ willingness to pay for tolls in the area based on their income levels were compared to determine vertical equity differences. Here, users' willingness to pay was estimated through a questionnaire survey on the travel time value based on the income level and matched with the income level of the area to determine residents' willingness to pay in the area.
RESULTS : This study reveals that there is a significant difference in social equity for road infrastructure use based on income level. This difference in the indexing was reflected in developing an indicator based on distribution equity.
CONCLUSIONS : The proposed vertical equity assessment method is relatively simple and can be utilized as a tool for establishing policies. As a basic tool for analyzing vertical equity in road pricing, it can be effectively applied to analyzing the vertical equity of road users in countries such as Japan, where tolls for highways are very high, and the United States, where tolls are charged in forms of Turnpike and HOT.
PURPOSES : In this study, the factors influencing traffic accidents of commercial vehicles in the transportation industry were examined. The evidence observed in this study showed how it contributes to the establishment of safety management policies.
METHODS : Safety management data obtained from the Korean Transportation Safety Authority were integrated. A multi-regression analysis was performed by comparing data for the past three years of traffic accident data.
RESULTS : Through multi-regression analysis, items that significantly influenced the safety evaluation index (the number of traffic accidents per vehicle owned and the number of dangerous driving actions per 100 km per person) were analyzed. Items with similar patterns observed for various commercial vehicle industries were also analyzed. Monthly average drop off rate, number of law violations per driver, percentage of drivers above 65 years old, percentage of drivers that have completed the compulsory education, number of vehicles owned, and driving distance per vehicle are the variables that influenced the safety evaluation index.
CONCLUSIONS : There is a growing need to establish safety management policies and management measures to enhance the voluntary safety management capabilities of the industry. Safety management should be conducted through the analysis of traffic accident impact factors for commercial vehicles.
PURPOSES : In this study, drone highway route alternatives were evaluated using the analytic hierarchy process (AHP) technique to investigate any difficulties or improvements while designing drone highway routes.
METHODS : Based on the literature review and AHP analysis, 39 road and airport experts were surveyed to evaluate two alternate drone highway routes that connect the Seoul train station and Jamsil park near Gangnam business district.
RESULTS : The AHP analysis results revealed that the environmental aspect was the most critical factor in designing a drone highway route, followed by social and technological factors. Among the investigated factors, noise and life-environment showed the highest geometric mean value of 0.21. This mean should be considered when developing plans and policies for drone highway design.
CONCLUSIONS : Environmental and social agreement is more crucial than the technological and economic aspects when designing drone highway routes. Laws and policies should be updated and followed to support the drone highway system, which is vital in logistics.
PURPOSES : The purpose of this study is to derive specific road design elements for safe urban underground and to adopt measures for minimizing traffic delays and to maintain efficient operation.
METHODS : In this study, a qualitative study was conducted using Focus Group Interview (FGI) method to identify significant connection characteristics and develop connections to urban underground roads. Finally, this study analyzes design elements necessary for traffic safety and efficient traffic operation. In addition, relevant case studies were performed with keywords from the FGI method results. Therefore, major design elements were analyzed for urban underground road connection and connection analysis for traffic simulation-based verification.
RESULTS : The main characteristics of the connection between the underground roads of the downtown area were divided into three types: traffic flow characteristics, geometric characteristics, and driver behavioral characteristics. From the review of 16 leading studies (10 domestic papers and 6 international papers) according to the characteristics, the main design factors for “traffic flow characteristics” include the traffic volume, design speed, heavy vehicle ratio, and lane change. The important design elements for “geometric characteristics” include the separation distance, number of lanes, slope, lane and shoulder width and the design factors for “driver behavioral characteristics” showed reaction time, driver vision, and driving speed. CONCLUSIONS : The FGI method identified the main characteristics of connections to the underground roads. In addition, the relevant empirical and theoretical research data were considered in case studies, and the design elements were derived and separated spatially based on the features of each design element, establishing a point-specific design element guideline.
PURPOSES : The aim of this study is to develop a decision-making model for safety countermeasures based on the characteristics of water deer roadkills.
METHODS : Through field investigation, 113 water deer roadkills with factors related to environment, geometry, and ecology were collected from May 2018 to April 2019. From the collected database, the characteristics of water deer roadkills were analyzed. An analytic hierarchy process was applied to establish a decision-making model to prevent water deer roadkills from appearing.
RESULTS : The likelihood of water deer roadkills increases in summer and winter, road sections in suburban areas with low traffic volume, surrounding farmlands, and areas without illumination. The results show that factors such as safety, ecology, road geometry, policy consistency, and the willingness of the local government are critical factors for establishing the decision-making model.
CONCLUSIONS : Appropriate safety countermeasures for water deer roadkills can be developed if the roadkill frequency, degree of sight distance restriction, speed limit for controlling overspeeding, roadkill severity, degree of forest area, traffic volume, and willingness of competent authorities are considered as essential variables.
PURPOSES : Arterial work zones, particularly at signalized intersections, have several characteristics and effects different from freeways. This paper presents three significant work zone effects on signalized intersections: (1) saturation headway change (saturation flow rate change), (2) green time (g/C ratio) change, and (3) progression speed degradation impacts on bandwidth performance.
METHODS : Both saturation flow rate reduction and g/C reduction were selected as the work zone impact variables for a signalized intersection, while bandwidth capacity reduction was chosen to measure the impact of work zones on arterials. The authors established a statistical model and normalized g/C table to estimate saturation headways and the g/C ratio at signalized intersection work zones based on the work intensity, pavement condition, ledge presence, turn percentages from shared lanes, and number of closed exclusive turn lanes. In addition, the dynamic bandwidth capacity and bandwidth solution space change based on the progression speed were introduced in this study.
RESULTS : A normalized g/C ratio distribution was developed to estimate both the non-work zone and work zone g/C ratios under different work zone configurations. The results of the estimated work zone capacity using the work zone saturation headway model and the g/C ratio distribution showed that the estimated capacity reduction ranged from 32.78%~2.93%. In addition, arterial dynamic bandwidth and its capacity were both critically influenced by the progression speed.
CONCLUSIONS : The proposed model and method will help practitioners understand the factors that cause a decrease in the saturation flow rate and g/C and influence progression quality on the urban arterial street due to work zones. Moreover, the proposed model and method can guide the calibration of simulation tools to properly represent the resulting capacity effects of work zones on arterial streets.