Documents published in Scipedia

• Functional Rescue of Dopaminergic Neuron Loss in Parkinsons Disease Mice After Transplantation of Hematopoietic Stem and Progenitor Cells

  W. Altarche-Xifro, U. Vicino, M. Muñoz-Martin, A. Bortolozzi, J. Bové, M. Vila, M. Cosma

  Collection of EBioMedicine (2017).

  
  

  Abstract

  Parkinsons disease is a common neurodegenerative disorder, which is due to the loss of dopaminergic neurons in the substantia nigra pars compacta (SNpc) and for which no definitive cure is currently available. Cellular functions in mouse and human tissues can be restored after fusion of bone marrow (BM)-derived cells with a variety of somatic cells. Here, after transplantation of hematopoietic stem and progenitor cells (HSPCs) in the SNpc of two different mouse models of Parkinsons disease, we significantly ameliorated the dopaminergic neuron loss and function. We show fusion of transplanted HSPCs with neurons and with glial cells in the ventral midbrain of Parkinsons disease mice. Interestingly, the hybrids can undergo reprogramming in vivo and survived up to 4 weeks after transplantation, while acquiring features of mature astroglia. These newly generated astroglia produced Wnt1 and were essential for functional rescue of the dopaminergic neurons. Our data suggest that glial-derived hybrids produced upon fusion of transplanted HSPCs in the SNpc can rescue the Parkinsons disease phenotype via a niche-mediated effect, and can be exploited as an efficient cell-therapy approach.

  Abstract
  Parkinsons disease is a common neurodegenerative disorder, which is due to the loss of dopaminergic neurons in the substantia nigra pars compacta (SNpc) and for which no definitive [...]

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• Pedestrian Traffic Operations in Urban Networks

  M. Zheng, T. Chase, J. Yan, S. Jun, V. Sisiopiku, L. Tian, Y. Zheng, X. Wang, B. Schroeder, Z. Qiu, L. Elefteriadou

  Collection of Transportation Research Procedia (2017).

  
  

  Abstract

  The pedestrian mode is an important component of urban networks, and greatly affects the performance of the sidewalks and crosswalks, as well as the entire network traffic operations by interacting with other traffic modes (automobile, bicycle, transit). There have been many studies concerning different aspects of pedestrian behaviors, such as pedestrian walking speed, pedestrian delay, gap acceptance, signal compliance, route choice, etc. The Highway Capacity Manual (HCM) included the pedestrian mode in the HCM 1994 (update to the HCM 1985) and the HCM, 2010 provided several basic technical methodologies for evaluating the pedestrian level of service (LOS) of different urban street facilities. However, it does not fully cover the pedestrian operation in a great detail and it is missing some important findings in recent studies. The objective of this paper is to provide an overview of pedestrian operations in urban networks, to identify the important aspects of pedestrian operation analysis and to provide recommendations for pedestrian facilities in the HCM on the basis of a summary of available U.S. and international literature. The following topics will be discussed: pedestrian movement models, pedestrian delay estimation, pedestrian-vehicle interactions, and pedestrian travel time estimation. The major features of pedestrian movement along urban segments are the walking speed and available space, which were well examined in past studies. Pedestrian delay is one important measure of pedestrian operation, and its estimation models at signalized/unsignalized intersections are presented with respect to different scenarios. Modifications to the delay model in the HCM, 2010 are highlighted. Pedestrian-vehicle interactions highly affect traffic operations. Both driver and pedestrian behaviors in such an interaction were observed in the field and were examined quantitatively. Pedestrian jaywalking behavior was also observed and its impact on traffic is discussed. Pedestrian route choice at the strategic level and crossing location selection at the operational level jointly determine the pedestrian moving path and further affect the travel time at path-level. A model for estimating pedestrian travel time in an urban network is developed and presented. Such a model can be used to evaluate the facility performance as well as serve for pedestrian route selection. This paper identifies the important aspects of pedestrian operation analysis in an urban network and provides several recommendations to the HCM.

  Abstract
  The pedestrian mode is an important component of urban networks, and greatly affects the performance of the sidewalks and crosswalks, as well as the entire network traffic [...]

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• Advanced Evaluation Methods for Variable Speed Limit Systems

  W. Ackaah, K. Bogenberger

  Collection of Transportation Research Procedia (2017).

  
  

  Abstract

  The variable speed limit (VSL) system has been implemented on many freeways and urban arterials as a link control strategy. Objectives for deploying VSL systems may include giving advance warning, stabilize and smooth traffic (i.e. harmonization). Accuracy and reliability of the messages displayed by VSL systems can “make or break” its successful implementation. The aim of this paper was to present methods for evaluating VSL systems. As VSL systems may be implemented with different control strategies, an approach for assessing different features of the system independently was adopted. In this way, systems with different control strategies can be evaluated. Methods for assessing incident detection, warning and harmonization abilities were presented. A case study on the VSL system on the Autobahn A99 near Munich, Germany was also discussed.

  Abstract
  The variable speed limit (VSL) system has been implemented on many freeways and urban arterials as a link control strategy. Objectives for deploying VSL systems may include [...]

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• Operational Impact of Horizontal and Vertical Alignment of Two-Lane Highways

  A. Moreno, C. Llorca, A. Garcia

  Collection of Transportation Research Procedia (2017).

  
  

  Abstract

  The Highway Capacity Manual (HCM) defines the level-of-service criteria for two-lane highways based on three performance measures: average travel speed (ATS), percent time spend following (PTSF) and percent of free-flow speed (PFFS). The performance measures are affected by the lack of passing opportunities, which is quantified through adjustment factors depending on the percentage of no passing zones. Passing zones are provided where available sight distance is greater than the minimum passing sight distance, and their length and frequency depend mainly on the physical constrains and cost limitations. HCM current evaluation of traffic performance excludes horizontal alignment variations, which could produce more or less sinuous alignments and thus affect potentially to both average travel speed and percentage time spent following. Moreover, HCM considers terrain type rather than the actual vertical profile, which could overestimate or underestimate the expected traffic performance depending on how accurately the roadway was adapted to the terrain. The objective of the research is to analyze the relationship between highway horizontal alignment, characterized by curvature change rate (CCR), highway vertical alignment, characterized by the gradient change rate, and traffic performance, based on ATS and PTSF. For the research, 25 Spanish two-lane rural highways were selected. Horizontal geometry was obtained from Google Earth using an azimuth-based restitution program. CCR was calculated and used to identify homogenous segments. Vertical alignment was recreated from GPS data. The sample included 112 homogeneous segments and 451 passing zones. After the geometry-based characterization, 20 homogeneous segments were introduced and simulated in the TWOPAS simulation model. TWOPAS was previously calibrated and validated with passing maneuvers data from Spanish highways. Traffic conditions (directional traffic volume, directional split and percentage of heavy vehicles) were varied. The analysis of the simulation results provided models of PTSF and ATS depending on CCR and gradient change rate, among other parameters. The results of this research will help highway designers and practitioners to predict operational performance based on CCR, type of gradient and expected hourly traffic volume, and could be used as management and design criteria.

  Abstract
  The Highway Capacity Manual (HCM) defines the level-of-service criteria for two-lane highways based on three performance measures: average travel speed (ATS), percent time [...]

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• A Local Non-restrictive Ramp Metering Strategy Based on Stochasticity of Capacity

  R. Trapp

  Collection of Transportation Research Procedia (2017).

  
  

  Abstract

  A local non-restrictive ramp metering strategy PRO is introduced. It is based on the stochasticity of capacity. The ramp metering algorithm shows innovative features: • upstream time shifted measurements for anticipation • measurements are actuated every second • up to three vehicles per green are allowed Details of the theory of this strategy are described in the first part. At freeway B27 three ramp meters with the PRO algorithm were installed. In the second part, based on extensive detailed traffic and accident data the effects on traffic flow and safety are described. The impact is positive regarding vehicle speed, queue duration and length as well as capacity and traffic safety. The improvements of speeds, travel times and capacities are statistically significant. The ramp metering systems are highly cost effective.

  Abstract
  A local non-restrictive ramp metering strategy PRO is introduced. It is based on the stochasticity of capacity. The ramp metering algorithm shows innovative features: • [...]

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• 2+1-roads Recent Swedish Capacity and Level-of-Service Experience

  T. Bergh, M. Remgård, A. Carlsson, J. Olstam, P. Strömgren

  Collection of Transportation Research Procedia (2017).

  
  

  Abstract

  The first Swedish 2+1 median barrier road was opened in 1998. The concept was to retrofit the standard existing two-lane 13 m paved width cross-section at 90 and 110 kph posted speed limit without widening. This design has one continuous lane in each direction, a middle lane changing direction every one to three kilometres with a median barrier separating the two traffic directions. Today over 2 700 km 2+1 median barrier roads are opened for traffic. AADT’s vary from some 3 000 to 20 000 with an average just below 10 000 nowadays normally with 100 kph. The concept has lately been enhanced also to cover the existing 9 m paved width cross-section. The design concept is the same from a driver’s viewpoint, one continuous lane in each direction with a middle lane changing direction and a separating median barrier. This is created by introducing a continuous median barrier and adding overtaking lanes within an overtaking strategy. The differences are the existence of 1+1-sections, less overtaking opportunities and a slightly more narrow cross-section. Some 15 projects are opened. The purpose of this paper is to summarize present knowledge on level-of-service issues as they are presented in Swedish design and assessment guidelines and to give an overview of field measurements and theoretical analytical and simulation studies supporting the recommendations.

  Abstract
  The first Swedish 2+1 median barrier road was opened in 1998. The concept was to retrofit the standard existing two-lane 13 m paved width cross-section at 90 and 110 kph posted [...]

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• Influence of Dynamic Traffic Control Systems and Autonomous Driving on Motorway Traffic Flow

  T. Wietholt, J. Harding

  Collection of Transportation Research Procedia (2017).

  
  

  Abstract

  As in many other countries, traffic demand on German motorways is continuously rising, especially during peak hours. Enhancing the road infrastructure by building additional lanes or new motorways is cost-intensive and - due to the complex planning process in Germany – extremely tedious. Thus, the government tries to maximise the performance of the existing infrastructure using dynamic control systems. The development and deployment of autonomous driven vehicles can have positive effects on the capacity of road elements. In this study the effect of dynamic control systems on the traffic flow on motorways is analysed in case studies using microscopic traffic simulation. Furthermore it is outlined that autonomous driving in an environment where access to the motorway is limited to autonomous vehicles only can have a positive effect in terms of higher capacities and more harmonized traffic resulting in fewer traffic breakdowns.

  Abstract
  As in many other countries, traffic demand on German motorways is continuously rising, especially during peak hours. Enhancing the road infrastructure by building additional [...]

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• Proposal and Application of Parking Area Performance Measurement Methodology

  T. Muramatsu, T. Oguchi

  Collection of Transportation Research Procedia (2017).

  
  

  Abstract

  The function of parking areas at expressway rest stops is to provide drivers with opportunities to park their vehicles for their own purposes, so the number of parking spots has been discussed. However, as the number of parking spots increases, the parking area becomes maze-like and the use of the parking spots becomes inefficient. This leads to skepticism that an increase in parking area capacity will contribute to enhancing parking area performance. Meanwhile, one vehicle is able to park in a parking spot when another vehicle exits the area that is fully occupied, so the condition of drop-by traffic at a rest stop can be discussed using the queuing theory by viewing a rest stop as a warehouse. Thus, this study aims to determine the applicability of the queuing theory when discussing drop-by traffic situations, while assuming a first-in first-out (FIFO) condition. For the applicability of the queuing theory of describing parking area performance, this study employed the ETC probe time-stamp data. The observed values from the ETC probe time-stamp data and FIFO assumed time lags are described, and the applicability of the observed ETC time-stamp data to representing the exact conditions was determined by comparing the number of vehicles parked on the hour every hour and those counted by the observed ETC probe time-stamp data. Finally, the applicability of the FIFO assumption was discussed using the correlation between the observed ETC probe time-stamp data and the FIFO assumed time lags calculated by the data. The results indicate that a FIFO assumption could alternate the observed the ETC probe time-stamp data. The number of vehicles staying on the hour every hour can be represented by the calculation results from FIFO assuming time lags. These findings show that it could be possible to determine the congregative situations of an expressway rest stop analyzed by the ingress and egress time-stamp records. Also, this result assumes any contribution to assessing the functional performance by measuring only the number of vehicles entering and exiting a parking area.

  Abstract
  The function of parking areas at expressway rest stops is to provide drivers with opportunities to park their vehicles for their own purposes, so the number of parking spots [...]

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• A Model for Capacity Reduction at Roadwork Zone

  P. Strömgren, J. Olstam

  Collection of Transportation Research Procedia (2017).

  
  

  Abstract

  This paper presents an investigation of capacity reduction in connection with roadwork. The paper presents a state-of-the-art description on roadwork effects on capacity. The state-of-the art has been used to develop a model for estimation of capacity reduction at roadwork zone on Swedish roads. The model has partly been validated with empirical data from a full scale test at the freeway network in Gothenburg. The studies presented in the literature shows that capacity differs not only between different roadwork designs but also between roadwork with similar design. Thus, one can conclude that there is a high variation between the roadwork zone due to effects of surrounding elements, such as the type of work and external effects such as rain (which affects the capacity even under normal conditions). The differences that exist in the estimation of capacity for motorway sections next to a roadwork zone can be said to consist of four situation-specific variables. These four variables are: the percentage of heavy vehicles, type of road, the width of the remaining lanes and diversion of traffic to the opposite carriageway. An increasing proportion of heavy vehicles have a negative impact on roadwork zone capacity. An increasing complexity of work, from light barrier works to extensive bridge repair, has a negative impact on performance. An increased lane width has a positive effect on capacity. The diversion of traffic to the opposite carriageway is often the cause of the bottleneck and therefore has a significance effect on capacity. The conclusion from the literature review is that the most important parameters that should be incorporated in a Swedish capacity manual for the operation and maintenance of roadwork are: the proportion of heavy traffic, lane width, type of roadwork, number of closed lanes, closed road shoulder, proportion of commuter traffic and length of roadwork zone. In general, there have been (too) few empirical studies focusing on the differences in capacity caused by these situation-specific variables. The paper presents a comparison between the Dutch model for computation of capacity reduction and a composite model of reduction factors from Germany, USA and Denmark. The comparison show that the two models essentially gives the same results. Based on these results a new model was developed. In the developed model, the capacity for the remaining lane is calculated. The paper presents results from a field study in Gothenburg where throughput was measured in three cases during a morning hour and one afternoon hour. The capacity was calculated from the normal site conditions according to historical traffic flow and speed data. The result shows that the empirically estimated confidence interval of capacity reduction is consistent with the reduction calculated with the new model for the different cases. The conclusion is that the model can be used to calculate capacity reductions for different roadwork zone configurations but that validation for more configurations is desirable.

  Abstract
  This paper presents an investigation of capacity reduction in connection with roadwork. The paper presents a state-of-the-art description on roadwork effects on capacity. [...]

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• Harmonization with Variable Speed Limits on Motorways

  P. Strömgren, G. Lind

  Collection of Transportation Research Procedia (2017).

  
  

  Abstract

  This paper presents an investigation and a state-of-the-art description of traffic effects of harmonization with variable speed limits. Expansion of the E4 south of Stockholm has been carried out during the years 2009-2013. The expansion includes a rearranged lane configuration within the existing road section (25 m) and traffic management systems. Previous design with two lanes and hard shoulder has been replaced with three lanes without shoulder. In addition, the road has been equipped with variable speed limits (with red ring), queue warning system with recommended speed and emergency refuge areas (ERAs). The queue warning functionality was activated in 2011 and harmonization in 2013. Reduced speed variance is an important goal for the traffic management system and is considered to both reduce rear-end collisions and the risk of capacity breakdown. German experience shows that harmonization affects capacity down to about 80 kph. English experience is that the harmonization and monitoring can reduce accidents by 40% at normal speed of 70 mph (112 kph). Germany and England decrease the speed with approximately 20 kph at the degree of saturation of 0.7 to let the flow be harmonized before the traffic density has increased too much. A measure to describe disturbed and undisturbed traffic can be the relative change in the standard deviation of the average speed for 5-minutes periods updated each minute, called CVS. In case of accidents, CVS may be twice as high as normal. The standard deviation of all vehicles is calculated for each minute and aggregated into five-minute periods. The harmonization settings on E4 south of Stockholm has been iteratively designed and ultimately set to 325 vehicles/5 min, which has worked well. The variable speed limit is reduced to 80 kph and stabilizes the flow. The harmonization indicates a potential risk of queue for the road users, which becomes more prepared if the queue warning is activated further along the road due low speed and the risk of sudden braking. The main results can be summarized as follows: • The average speed during rush hour on weekdays has increased by 2.5 kph after the installation of the traffic control system, of which 25% is assumed to be attributable to the traffic management system • The harmonization has delayed the onset of collapse. During the periods in which harmonization has not been activated but there has been a breakdown, it is considered that harmonisation would have passed the half period and then collapse would occurred. • The accidents have been reduced by half, of which 25% is assumed to depend on traffic management (harmonization, queue warning and VMS) The queue warning has worked well, but could be improved by also exploiting the so-called CVS. The measure reveals the instabilities in the flow, sometimes tens of minutes before the AID-alarm due low speeds is enabled. In rush hour when traffic is dense (> 325 vehicles/5 min) and harmonization has already been activated the CVS measure gives further information, which could be exploited to improve the queue warning algorithm.

  Abstract
  This paper presents an investigation and a state-of-the-art description of traffic effects of harmonization with variable speed limits. Expansion of the E4 south of Stockholm [...]

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