| 1. |
- Karim, Hawzheen, 1973-, et al.
(författare)
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Life-cycle Cots Analyses for Road Barriers
- 2011
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Ingår i: Journal of transportation engineering. - 0733-947X .- 1943-5436.
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Tidskriftsartikel (refereegranskat)abstract
- This study aimed at applying and evaluating a new approach for analyzing life-cycle costs for road components during the road planning and design process. Road median barriers were chosen as an example. The approach is based on a method called "Activity-Based Life-Cycle Costing using the Monte Carlo Simulation" for managing future costs and the associated risks. The results show a potential for increasing efficiency throughout the road planning and design process by minimizing the life-cycle costs of road components. The results also show that implementation of life-cycle cost analyses in the road planning and design process is possible, but difficult, mainly due to lack of relevant data.
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| 2. |
- Karim, Hawzheen, 1973-, et al.
(författare)
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Road Barrier Repair Costs and Influencing Factors
- 2011
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Ingår i: Journal of transportation engineering. - 0733-947X .- 1943-5436. ; 137:5, s. 349-359
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Tidskriftsartikel (refereegranskat)abstract
- This paper presents a study that examines repair costs for different road barrier types and factors that influence these costs. The analyses focused on w-beam and cable barriers used as median barriers. To some extent, pipe barriers, Kohlswa-beam barriers and concrete barriers were also studied. The influencing factors included in this study were: road type, speed limit, barrier type and seasonal effects. A case study was conducted in four regions of the Swedish Road Administration. Data were collected from 1625 barrier repairs carried out during 2005 and 2006. The results show that the number of barrier repairs and the average repair cost per vehicle kilometre are higher along collision-free roads than along motorways and 4-lane roads. The results also show that the number of barrier repairs and the average repair cost per vehicle kilometre are higher for cable barrier than for other barrier types. No conclusion can be drawn regarding influence of speed limits on barrier repairs and associated costs as the result from the regions are divergent and not statistically significant.
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| 3. |
- Lina, Nordin, et al.
(författare)
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Road surface wetness variations : Measurements and effects for winter road maintenance
- 2013
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Ingår i: Journal of transportation engineering. - 0733-947X .- 1943-5436. ; 139:8, s. 787-796
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Tidskriftsartikel (refereegranskat)abstract
- Road wetness is a critical parameter when it comes to preventing road slipperiness. It has so far been difficult to measure, but new measurement techniques on the market make it useful to investigate the savings opportunities within road maintenance operations. The present study tests a new sensor mounted on a road maintenance vehicle run in a maintenance district in central Sweden. The sensor that measures road surface water depth is connected to a global positioning system (GPS) system and a global system for mobile communications (GSM) phone modem. Potential savings are calculated based on the measured road surface water depth and on the amount of applied salt needed to lower the freezing point to a certain degree. The results indicate variations in water depth along the measured roads, which implies that the salt concentrations along the roads could also vary. Though the variations were smaller along the tested highway, the calculated savings could still be up to 22%. Despite the many assumptions made in the calculations, considerable savings could potentially be realized by applying such wetness measurements.
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| 4. |
- Mwesige, Godfrey, et al.
(författare)
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A Model and Its Applications for Predicting Passing Rate at Passing Zones on Two-Lane Rural Highways
- 2016
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Ingår i: Journal of transportation engineering. - : American Society of Civil Engineers (ASCE). - 0733-947X .- 1943-5436. ; 142:3
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Tidskriftsartikel (refereegranskat)abstract
- Passing zones are designed to provide sufficient sight distance for fast vehicles to pass safely slow vehicles and contribute to operational efficiency of two-lane highways. However, lack of suitable models to predict passing rate and capacity has made it difficult to quantify operational benefits of passing zones. In this paper, a model is proposed to predict passing rate in the subject direction at passing zones using traffic and geometric factors. The model is developed based on speed and passing data collected at 19 passing zones in Uganda using pneumatic tube classifiers and video recordings. Findings show that passing rates depend on the length of the passing zone, absolute vertical grade, traffic volume in two travel directions, directional split, 85th percentile speed of free-flow vehicles and percent heavy vehicles in the subject direction. The peak passing rate also referred to as the passing capacity occurs at 200, 220, and 240 vehicles/h in the subject direction for 50/50, 55/45, and 60/40 directional splits, respectively. The model could potentially be applicable in planning, design, and safety evaluation of two-lane rural highways.
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| 5. |
- Nordin, Lina, 1981, et al.
(författare)
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Road Surface Wetness Variations: Measurements and Effects for Winter Road Maintenance
- 2013
-
Ingår i: Journal of Transportation Engineering. - : American Society of Civil Engineers (ASCE). - 0733-947X .- 1943-5436. ; 139:8, s. 787-796
-
Tidskriftsartikel (refereegranskat)abstract
- Road wetness is a critical parameter when it comes to preventing road slipperiness. It has so far been difficult to measure, but new measurement techniques on the market make it useful to investigate the savings opportunities within road maintenance operations. The present study tests a new sensor mounted on a road maintenance vehicle run in a maintenance district in central Sweden. The sensor that measures road surface water depth is connected to a global positioning system (GPS) system and a global system for mobile communications (GSM) phone modem. Potential savings are calculated based on the measured road surface water depth and on the amount of applied salt needed to lower the freezing point to a certain degree. The results indicate variations in water depth along the measured roads, which implies that the salt concentrations along the roads could also vary. Though the variations were smaller along the tested highway, the calculated savings could still be up to 22%. Despite the many assumptions made in the calculations, considerable savings could potentially be realized by applying such wetness measurements. (C) 2013 American Society of Civil Engineers.
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| 6. |
- Othman, Sarbaz Najib, 1971, et al.
(författare)
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Safety Analysis of Horizontal Curves Using Real Traffic Data
- 2014
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Ingår i: Journal of Transportation Engineering. - : American Society of Civil Engineers (ASCE). - 0733-947X .- 1943-5436. ; 140:4
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Tidskriftsartikel (refereegranskat)abstract
- Researchers are still seeking a better understanding of the parameters that affect safety in horizontal curves. Curves are one of the most critical sections of the road network contributing to a high percentage of serious runoff accidents and lane-changing crashes. Moreover, driving in curves requires combined control of both steering and speed, taking into account the dynamic response and limits of the car. The objectives of this study were to evaluate the safety performance of horizontal curves by analyzing vehicle dynamic signals, such as lateral acceleration and speed, as well as quantitative analysis of lane-changing maneuvers. The study uses real traffic environments where driver behavior and vehicle response data were recorded and stored during regular operations without subjecting the driver to any experimental controls. A total of 96 curves, equally distributed for left and right turn directions, have been collected and grouped according to their radii. The analysis identified frequent overtaking and lane-change maneuvers on the curves, of which 20% more lane changes occurred on right curves than on left curves. Lane-change maneuvers also increased significantly with increasing curve radius. The curve entrance was found to be the most dangerous segment of a curve. Current design practice assumes the safety risk is constant when driving along horizontal curves. The results also showed that drivers consider curve radius in choosing their driving speed rather than the posted speed limit of the curves. The study showed how road design influences the driver's strategy by establishing links between curve features, vehicle dynamic responses, and the driver's behavior. Analyzing road characteristics gave insight into how road geometry affects the vehicle dynamics relevant to safety and driving strategy through curves. The findings are useful inputs for reviewing curve design, selecting appropriate countermeasures, and improving active safety devices.
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| 7. |
- Othman, Sarbaz Najib, 1971, et al.
(författare)
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Using Naturalistic Field Operational Test Data to Identify Horizontal Curves
- 2012
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Ingår i: Journal of Transportation Engineering. - : American Society of Civil Engineers (ASCE). - 0733-947X .- 1943-5436. ; 138:9, s. 1151-1160
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Tidskriftsartikel (refereegranskat)abstract
- Investigations to identify relationships between crashes and road features usually deal with effects of only one or two of the main components of traffic safety, i.e., human, vehicle, and infrastructure performance. There are several contributing factors of the components that together lead to a crash. This study devises an approach to include information from all three components in a system using field operational test (FOT) data. FOT data are recorded from real-life driving that is different from traffic simulations and specific on-site data collection. The study focuses on identifying horizontal curves using FOT and provides access to vehicle and human response data at the exact time when the vehicle drove in a specific location. A method has been developed to derive path radius and to identify start-end points of horizontal curves using FOT data. With this information, vehicle response signals and human behavior data can then be arranged on a common axis referenced to the curve. The approach also identifies lane changing maneuvers on curves that can be used to evaluate potential crash triggers. The application of this method allows for reviewing changes in the regulatory speed limit, curve geometry, or crash history and thus evaluates the design of curves and choosing appropriate countermeasures.
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| 8. |
- Othman, Sarbaz, et al.
(författare)
-
Safety analysis of horizontal curves using real traffic data
- 2011
-
Ingår i: Journal of transportation engineering. - : American Society of Civil Engineers (ASCE). - 0733-947X .- 1943-5436. - 9789173855853 ; 140:4
-
Tidskriftsartikel (refereegranskat)abstract
- Researchers are still seeking a better understanding of the parameters that affect safety in horizontal curves. Curves are one of the most critical sections of the road network contributing to a high percentage of serious runoff accidents and lane-changing crashes. Moreover, driving in curves requires combined control of both steering and speed, taking into account the dynamic response and limits of the car. The objectives of this study were to evaluate the safety performance of horizontal curves by analyzing vehicle dynamic signals, such as lateral acceleration and speed, as well as quantitative analysis of lane-changing maneuvers. The study uses real traffic environments where driver behavior and vehicle response data were recorded and stored during regular operations without subjecting the driver to any experimental controls. A total of 96 curves, equally distributed for left and right turn directions, have been collected and grouped according to their radii. The analysis identified frequent overtaking and lane-change maneuvers on the curves, of which 20% more lane changes occurred on right curves than on left curves. Lane-change maneuvers also increased significantly with increasing curve radius. The curve entrance was found to be the most dangerous segment of a curve. Current design practice assumes the safety risk is constant when driving along horizontal curves. The results also showed that drivers consider curve radius in choosing their driving speed rather than the posted speed limit of the curves. The study showed how road design influences the driver's strategy by establishing links between curve features, vehicle dynamic responses, and the driver's behavior. Analyzing road characteristics gave insight into how road geometry affects the vehicle dynamics relevant to safety and driving strategy through curves. The findings are useful inputs for reviewing curve design, selecting appropriate countermeasures, and improving active safety devices.
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| 9. |
- Othman, Sarbaz, et al.
(författare)
-
Using naturalistic field operational test (FOT) data to identify horizontal curves
- 2011
-
Ingår i: Journal of transportation engineering. - Göteborg : American Society of Civil Engineers (ASCE). - 0733-947X .- 1943-5436. - 9789173855853 ; 138:9, s. 1151-1160
-
Tidskriftsartikel (refereegranskat)abstract
- Investigations to identify relationships between crashes and road features usually deal with effects of only one or two of the main components of traffic safety, i.e., human, vehicle, and infrastructure performance. There are several contributing factors of the components that together lead to a crash. This study devises an approach to include information from all three components in a system using field operational test (FOT) data. FOT data are recorded from real-life driving that is different from traffic simulations and specific on-site data collection. The study focuses on identifying horizontal curves using FOT and provides access to vehicle and human response data at the exact time when the vehicle drove in a specific location. A method has been developed to derive path radius and to identify start-end points of horizontal curves using FOT data. With this information, vehicle response signals and human behavior data can then be arranged on a common axis referenced to the curve. The approach also identifies lane changing maneuvers on curves that can be used to evaluate potential crash triggers. The application of this method allows for reviewing changes in the regulatory speed limit, curve geometry, or crash history and thus evaluates the design of curves and choosing appropriate countermeasures.
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| 10. |
- Silvano, Ary Pezo, et al.
(författare)
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Impact of Speed Limits and Road Characteristics on Free-Flow Speed in Urban Areas
- 2016
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Ingår i: Journal of transportation engineering. - 0733-947X .- 1943-5436. ; 142:2
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Tidskriftsartikel (refereegranskat)abstract
- The paper documents studies of posted speed limit (PSL) changes on the free-flow speed on urban roads. Before and after field measurements were conducted, changing the existing PSL from 50 to 40 or 60 km/h. The analysis was conducted on the mean free-flow speed difference and speed variability. The data collected were also used for multiple regression analysis, including PSL changes and selected self-explaining road characteristics. The results showed that a decreased PSL caused a small (1.6 km/h) but significant reduction in the mean free-flow speed and speed variance, which might lead to a 10% reduction of severe injury accidents. Furthermore, the PSL reduction had a larger impact on faster drivers and higher road network classes. Conversely, an increased PSL resulted in a 2.6 km/h increase in the mean free-flow speed but no change on speed variability. The regression results indicated that the free-flow speed was heavily influenced by road characteristics, such as carriageway width, road environments, and the presence of on-street parking and sidewalks. Arterial roads presented the largest impact. The PSL had a relatively small impact.
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| 11. |
- Svenson, Kristin
(författare)
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Estimated lifetimes of road pavements in Sweden using time-to-event analysis
- 2014
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Ingår i: Journal of transportation engineering. - 0733-947X .- 1943-5436. ; 140:11
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Tidskriftsartikel (refereegranskat)abstract
- Maintenance planning of road pavement requires reliable estimates of roads' lifetimes. In determining the lifetime of a road, this study combines maintenance activities and road condition measurements. The scope of the paper is to estimate lifetimes of road pavements in Sweden with time-to-event analysis. The model is stratified according to traffic load and includes effects of pavement type, road type, bearing capacity, road width, speed limit, stone size, and climate zone. Among the nine analyzed pavement types, stone mastic had the longest expected lifetime with a hazard ratio (risk of needing maintenance) estimated to be 36% lower than asphalt concrete. Among road types, 2+1 roads had 22% higher hazard ratio than ordinary roads indicating significantly lower lifetimes. Increased speed lowered the lifetime, while increased stone size (up to 20 mm) and increased road width lengthened the lifetime. The results are of importance for life-cycle cost analysis and road management. (C) 2014 American Society of Civil Engineers.
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| 12. |
- Bäckström, Magnus
(författare)
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Ground temperature in porous pavement during freezing and thawing
- 2000
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Ingår i: Journal of transportation engineering. - 0733-947X .- 1943-5436. ; 126:5, s. 375-381
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Tidskriftsartikel (refereegranskat)abstract
- Porous pavements are widely used for local disposal of storm water. This paper presents the results of a full-scale study of ground temperatures in porous pavement during periods with prolonged freezing conditions and during snowmelt. The pavement construction was situated in a housing area in Lulea in northern Sweden, and it consisted of porous asphalt over an aggregate base of macadam. It was found that the cooling of the porous pavement was governed by variations in ambient air temperature and that freezing of the soil below the subgrade was related to the freezing index. The porous pavement was more resistant to freezing than a conventional impermeable pavement due to higher water content in the underlying soil, which increased the latent heat in the ground. Thawing of the porous pavement was a rapid process, which depended on meltwater infiltration. The thawing process in a comparable impermeable pavement was slower.
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| 13. |
- Karim, Hawzheen, et al.
(författare)
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Road Design for Future Maintenance Problems and Possibilities
- 2008
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Ingår i: Journal of transportation engineering. - 0733-947X .- 1943-5436. ; 134:12, s. 523-531
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Tidskriftsartikel (refereegranskat)abstract
- This paper presents an investigation conducted to identify obstacles that prevent sufficient consideration of future road maintenance needs during the road planning and design phase. The investigation focuses on the road planning and design process within the Swedish Road Administration. For this reason the results are applicable for Nordic conditions concerning road design, maintenance, and climate. However, the results focus on general aspects of the planning and design process and ought to also be valid for other conditions outside the Nordic countries. The investigation was carried out using a method called "change analysis," which consists of complementary steps for the analysis of problems, processes, and goals in order to identify necessary changes. The investigation identified several problems within the road planning and design process related to consulting, knowledge, planning and design activities, regulations, organization structure, and demands from other authorities. The identified problems, activities within the planning and design process, and goals for the process were analyzed. Based on these analyses the investigation identifies the most urgent needs for change in order to eliminate the problems that result in insufficient consideration of maintainability during the planning and design process.
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| 14. |
- Lundkvist, Sven-Olof, et al.
(författare)
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Prediction of road marking performance
- 2007
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Ingår i: Journal of transportation engineering. - 0733-947X .- 1943-5436. ; 133:6, s. 341-346
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Tidskriftsartikel (refereegranskat)abstract
- From the road user's point of view the night-time visibility of road markings during wet conditions is of great importance, and instruments aimed for mobile measurement of the retroreflectivity of road markings are available. However, due to splash from the tires of the measuring vehicle, it is almost impossible to carry out measurements on wet road markings. The purpose of this study was to investigate if results obtained on dry road markings can be used for prediction of the retroreflectivity of wet markings. Furthermore, the possibility of predicting skid resistance of wet road markings from results obtained on dry road markings was examined. Physical measurements of a number of performance parameters of road markings showed that the retroreflectivity of a dry road marking surface and mean profile depth (texture) of the surface in question can be used both for prediction of retroreflectivity and skid resistance of wet road markings. As retroreflectivity and texture can be measured using mobile equipment, wet performance parameters can be estimated from measurements carried out on dry markings at speed. The precision of the models was found to be acceptable, which means that they seem to be useful for classifying performance of road markings. Based on the models, performance classes for retroreflectivity and skid resistance of wet road markings are proposed.
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| 15. |
- Offrell, Petra, et al.
(författare)
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Repeatability in crack data collection on flexible pavements : Comparision between surveys using video cameras, laser cameras, and a simplified manual survey
- 2005
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Ingår i: Journal of transportation engineering. - 0733-947X .- 1943-5436. ; 131:7, s. 552-562
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Tidskriftsartikel (refereegranskat)abstract
- Crack data can be collected using manual or automatic surveys. Traditionally, manual methods are used, and they are still the most common. Changing into automatic systems will enhance the efficiency of data collection as well as the objectivity. In this study the repeatability of an automatic crack data collection system using video images was evaluated. Ten repetitive measurements were made on a 10-km-long road section. Cracking was measured using six laser cameras attached to the same vehicle.The results from the two methods were compared. Simultaneously, a simplified manual windshield survey was conducted by three different persons, and the repeatability obtained was used for comparison with the repeatability established using the image and laser method, respectively. The correlation between repeated measurements using the two automatic systems was high, while the repeatability for the manual, subjective method was low. Suitable measures for crack characterization are discussed.
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| 16. |
- Poulikakos, L., et al.
(författare)
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Interpretation of Accelerated Laboratory Testing of the Prototype Modulas Stress in Motion (SIM) Sensor with the MMLS3 Load Simulator
- 2008
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Ingår i: Journal of transportation engineering. - 0733-947X .- 1943-5436. ; 134:10, s. 414-422
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Tidskriftsartikel (refereegranskat)abstract
- With modern heavy vehicles using higher inflation pressures and higher axle loads the dynamic measurement of the tire-pavement contact force/stress is essential not only for tire development but also in road research for the investigation of factors which may lead to excessive damage of pavements. In this paper the results of laboratory tests with a prototype stress in motion (SIM) quartz sensor trafficked with a one-third scale load simulator (MMLS3) are presented. The tests were designed to vary parameters such as tire inflation pressure, speed, ambient temperature, lateral position, and angle to direction of travel in a controlled environment in order to isolate the influence of these parameters on the SIM sensor results. All other controllable variables remained constant while the target parameter was varied. Tire inflation pressures were calculated from these data. The laboratory tests show that the prototype sensor promises to be an effective investigative tool for SIM measurements.
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| 17. |
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| 18. |
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| 19. |
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| 20. |
- Thomas, Fridtjof
(författare)
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Statistical Approach to Road Segmentation
- 2003
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Ingår i: Journal of transportation engineering. - 0733-947X .- 1943-5436. ; 129:3, s. 300-308
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Tidskriftsartikel (refereegranskat)
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| 21. |
- West, Jens, et al.
(författare)
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Individual and Synergetic Effects of Transit Service Improvement Strategies : Simulation and Validation
- 2017
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Ingår i: Journal of transportation engineering. - : American Society of Civil Engineers (ASCE). - 0733-947X .- 1943-5436. ; 143:6
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Tidskriftsartikel (refereegranskat)abstract
- Assessment of transit service improvements such as bus lanes, allowing boarding through all doors, and headway-based holding control requires detailed simulation capabilities. However, because the usage of models advanced enough to simultaneously analyze physical and operational measures has been limited, their validity has hitherto remained low. This paper assesses the implementation of several bus service improvement measures in a simulation model. The paper analyzes the effect of isolated and combinations of measures, and validates the model using field experiment data. The model predicted travel time improvements accurately (1–2% difference), while overestimating some of the headway variability effects. The three tested measures exercised negative synergy effects, with their combined effect being smaller than the sum of their marginal contributions, except for headway-based holding, which exercised positive synergy effects with the two other measures.
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| 22. |
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| 23. |
- Hagring, Ola
(författare)
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Estimation of parameters in distribution of headways in roundabouts
- 2002
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Ingår i: Journal of Transportation Engineering. - 1943-5436. ; 128:5, s. 403-411
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Tidskriftsartikel (refereegranskat)abstract
- Estimation of parameters in the distribution of headways in roundabouts is a cumbersome task. Inherent to data employed are temporal variation together with dependence between successive vehicles. This is a consequence of the sampling period and interactions in the roundabouts. The elimination of observations, so as to obtain trend-free samples of independent vehicles, removes too much information from the data. If all the observations are used, the results of the parameter estimations are affected by temporal variation and dependence between headways. In this paper, an analysis of the statistical properties of the headways between major stream vehicles in roundabouts is described. The properties investigated were the existence of temporal variation in the measured headways and independent and identically distributed successive headways, i.e., if the headways were from a random sample. More than 50% of the investigated subsets suffered from trends or other nonrandom variations. The question whether these subsets should be excluded or not is discussed. Three methods for the estimation of parameters in the M3 distribution were tested. For the two-lane subsets, it was possible to demonstrate a linear relationship between the proportion of free vehicles and the volume. For the one-lane subsets, the adjusted R-2 was low, and the linear constant was not significant. Nevertheless, the distributions estimated by use of the two-lane subsets did not provide a better fit to the observed data than the distributions estimated by the use of one-lane subsets. The predicted capacity for a minor lane, i.e., the capacity obtained by the fitted distribution, was close to the capacity obtained by the empirical distribution function (the estimated capacity).
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| 24. |
- Karim, Hawzheen, et al.
(författare)
-
Road Design for Future Maintenance Problems and Possibilities
- 2008
-
Ingår i: Journal of Transportation Engineering. - 0733-947X. ; 134, s. 523-531
-
Tidskriftsartikel (refereegranskat)abstract
- This paper presents an investigation conducted to identify obstacles that prevent sufficient consideration of future road maintenance needs during the road planning and design phase. The investigation focuses on the road planning and design process within the Swedish Road Administration. For this reason the results are applicable for Nordic conditions concerning road design, maintenance, and climate. However, the results focus on general aspects of the planning and design process and ought to also be valid for other conditions outside the Nordic countries. The investigation was carried out using a method called ￜchange analysis,ￜ which consists of complementary steps for the analysis of problems, processes, and goals in order to identify necessary changes. The investigation identified several problems within the road planning and design process related to consulting, knowledge, planning and design activities, regulations, organization structure, and demands from other authorities. The
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