Showing papers by "California Department of Transportation published in 2013"
TL;DR: In this article, the authors investigated the feasibility of combining reflective and permeable pavements for addressing the built environment issues related to both heat island mitigation and stormwater runoff management, and showed that full depth permeable paving can carry both light-duty traffic and heavy-duty vehicles while retaining the runoff volume captured from an average California storm event.
Abstract: To help address the built environmental issues of both heat island and stormwater runoff, strategies that make pavements cooler and permeable have been investigated through measurements and modeling of a set of pavement test sections. The investigation included the hydraulic and thermal performance of the pavements. The permeability results showed that permeable interlocking concrete pavers have the highest permeability (or infiltration rate, ~0.5 cm s -1 ). The two permeable asphalt pavements showed the lowest permeability, but still had an infiltration rate of ~0.1 cm s -1 , which is adequate to drain rainwater without generating surface runoff during most typical rain events in central California. An increase in albedo can significantly reduce the daytime high surface temperature in summer. Permeable pavements under wet conditions could give lower surface temperatures than impermeable pavements. The cooling effect highly depends on the availability of moisture near the surface layer and the evaporation rate. The peak cooling effect of watering for the test sections was approximately 15–35?°C on the pavement surface temperature in the early afternoon during summer in central California. The evaporative cooling effect on the pavement surface temperature at 4:00 pm on the third day (25 h after watering) was still 2–7?°C lower compared to that on the second day, without considering the higher air temperature on the third day. A separate and related simulation study performed by the University of California Pavement Research Center (UCPRC) showed that full depth permeable pavements, if designed properly, can carry both light-duty traffic and certain heavy-duty vehicles while retaining the runoff volume captured from an average California storm event. These preliminarily results indicated the technical feasibility of combined reflective and permeable pavements for addressing the built environment issues related to both heat island mitigation and stormwater runoff management.
233 citations
TL;DR: The development of a novel wireless structural monitoring system specifically tailored for large-scale civil infrastructure systems by architecturally combining dense wireless sensor networks with a suite of information technologies remotely accessible by the Internet is reported on.
Abstract: Dense networks of low-cost wireless sensors have the potential to facilitate prolific data collection in large and complex infrastructure at costs lower than those historically associated w...
91 citations
TL;DR: Findings from evaluating performances of three different methods for segmenting freeway sites revealed that CRP method has the lowest false positive rate and significantly varied when different sets of SPFs were used while that of CRP was less affected.
34 citations
TL;DR: The results show that the predictive accuracy of the auto-regression models generally increases when more lags or past conditions are used, and are able to provide more accurate predictions than other models.
Abstract: In this paper, an auto-regression method is applied to pavement performance modelling to improve the predictive accuracy of predictions when there are only limited or incomplete data available. Using age and past measured conditions as independent variables, the average trend within a pavement group is captured by a ‘global’ function shared by all pavements, while any pavement-specific effects are reflected through the past pavement conditions involved in the model. In a case study, different auto-regression models with varying lags are developed based on measured pavement condition data and the predictive accuracy of the models is studied. The models are also compared with the traditional regression models, such as the shifted family curve and individual regression curves. The results show that the predictive accuracy of the auto-regression models generally increases when more lags or past conditions are used. The auto-regression models are able to provide more accurate predictions than other models. It ...
22 citations
TL;DR: Simple control logic for issuing speed advisories to drivers as they approach a queue could assist freeway managers in selecting suitable advisories so as to diminish the empirical estimate of collision likelihood at a specified time in the immediate future and by some target amount.
Abstract: Findings from previous studies indicate that a freeway traffic collision is more likely to occur in close physical proximity to the tail of a queue. The implication is that collision likelihood increases when drivers abruptly alter their trajectories (e.g., by decelerating or changing lanes) on encountering the queue. The implication is supported and bolstered with new and detailed data that were painstakingly extracted from two freeway stretches in California. These data show how the likelihood of collision increases as both the spatial and the temporal proximities to the tail of an expanding or receding queue become smaller. It follows that collision risk may be reduced by instructing drivers to begin decelerating while still upstream of queues. Retarding vehicle progress toward a queue's tail could retard the rate by which the likelihood of collision grows with time. Having vehicles approach a queue at diminished speeds may diminish the expected severity of a collision, should one still occur. This inf...
20 citations
TL;DR: In this article, the authors discuss some of the unique aspects and lessons of the New Zealand post-earthquake building safety inspection program that was implemented following the Canterbury earthquake sequence of...
Abstract: The authors discuss some of the unique aspects and lessons of the New Zealand post-earthquake building safety inspection program that was implemented following the Canterbury earthquake sequence of...
17 citations
TL;DR: It is shown that the computed statistical distributions of the bridge response can provide a quantitative baseline through which to facilitate the early detection of any anomalies indicative of a possible structural deterioration resulting from fatigue (service loads) or extreme loading events, i.e., earthquakes, artificial hazards, or other natural hazards.
Abstract: The long-range monitoring of civil infrastructure systems monitored with dense sensor arrays that are capable of generating voluminous amounts of data from continuous online monitoring requires the implementation of a proper data processing and archiving scheme to maximize the benefits of structural health monitoring operations. This paper focuses on the areas of data management, data quality control, and feature extraction of meaningful parameters to describe the response of large-scale infrastructure systems to ambient excitation in the context of structural health monitoring (SHM). Recordings from the monitoring system installed on the Vincent Thomas Bridge (VTB) in San Pedro, California form the database of the proposed data-management and archiving methodology. The data processing methodology for the VTB is based on the calculation of the sensor array acceleration covariance matrices for every hour of available data and the subsequent orthogonal decomposition of the covariance matrices. The dominant proper orthogonal modes of the bridge are determined, and their statistical variations over an extended observation period covering several months of continuous data are quantified and analyzed. The empirical probability density functions for the mean daily bridge accelerations are computed and used to compare the statistical variations in different periods of operation of the bridge (working days, weekends, holidays). It is shown that the computed statistical distributions of the bridge response can provide a quantitative baseline through which to facilitate the early detection of any anomalies indicative of a possible structural deterioration resulting from fatigue (service loads) or extreme loading events, i.e., earthquakes, artificial hazards, or other natural hazards.
16 citations
TL;DR: In this paper, the authors present recent technological and procedural innovations in evaluating multiple bids for a statewide survey of California pavement condition data, including evaluation on an item-by-item basis instead of comparing a derived composite index, combining several independent measurements of the same item to improve the quality of ground truth results and synchronisation of profiles and pavement images to strengthen the credibility of assessment.
Abstract: High-quality pavement condition data are fundamental to pavement management, but the collection of these data is costly and time-consuming with steadily increasing complexity in equipment and procedures. Evaluating the technical competence of an automated pavement condition survey service provider presents unique challenges to highway agencies, because the technologies are rapidly advancing and the technical details are often outside the skill set of pavement engineers and managers. This study presents recent technological and procedural innovations in evaluating multiple bids for a statewide survey of California. These include evaluation on an item-by-item basis instead of comparing a derived composite index, combining several independent measurements of the same item to improve the quality of ground truth results and the synchronisation of profiles and pavement images to strengthen the credibility of assessment.
9 citations
TL;DR: In this article, various existing methodologies that are used to size the queue storage at metered on-ramps were first reviewed and it was found that queue storage sized using 7% of peak hour onramp demand is widely accepted in practice, and detailed sizing guidance was developed in the highway geometric design policy of the American Association of State Highway and Transportation Officials.
Abstract: Queue storage at a metered freeway on-ramp is an essential design element for metered on-ramps to prevent on-ramp queue from extending beyond on-ramps. In this paper, various existing methodologies that are used to size the queue storage at metered on-ramps were first reviewed. It was found that queue storage sized using 7% of peak hour on-ramp demand is widely accepted in practice. A limited dataset collected in California helps provide some reality check for this method. It is recommended that queue storage be recognized as an indispensable design element at metered on-ramps, and detailed sizing guidance be developed in the highway geometric design policy of the American Association of State Highway and Transportation Officials (AASHTO).
9 citations
TL;DR: In this paper, an exact analytic framework is formulated with derived equations the first time to calculate the sight distance on a 3D compound curve in the presence of a median barrier, a roadside barrier, or a temporary cushion or barrier used for construction or other maintenance purposes.
Abstract: The sight distance (SD) on a three-dimensional (3-d) compound curve has been studied recently in the absence of obstacles at road sides. Often, physical barriers are installed at road sides or in a roadway median for reducing potential collision severities; these rigid, semi-rigid, or even temporary cushion-type barriers can limit or reduce the driver's sight distance, depending on their horizontal offset distances away from the nearest edge of traveled way (ETW). The closer a barrier to the ETW is, the shorter the driver's sight distance would be. Since most barriers are constructed to prevent running-off road or crossing-median collisions, it is crucial to check whether the installation would reduce the driver's sight distance and potentially cause other traffic collisions such as rear-end or side swipe collisions. In this paper, an exact analytic framework is formulated with derived equations the first time to calculate the sight distance on a 3-d compound curve in the presence of a median barrier, a roadside barrier, or a temporary cushion or barrier used for construction or other maintenance purposes. This framework provides an engineer a handy tool to examine the possible change of SD in the presence of a barrier and choose the required horizontal offset/clearance of a barrier from the nearest traveled way edge to meet certain design criteria or standards. This critical offset distance determined using this framework not only reinforces the importance of having roadside clearance recovery zones on highways but also provides a method to determine its horizontal clearance from a different standpoint. This analytic framework can easily be programmed into an Excel spreadsheet to evaluate the design of a physical barrier and its potential influence on sight distance along a 3-d compound horizontal and vertical curve. Transportation engineers or practitioners may find this design tool handy and useful once the programmed spreadsheet is saved in a shared or a flash/thumb drive. Note that the sight distance on a two-dimensional curve, such as a horizontal or a vertical curve, can be calculated straightforward as special cases using the programmed spreadsheet.
7 citations
TL;DR: In this paper, the authors provide an update of the major improvement in terms of ramp metering design and operations in California, including policies, development plans, and system management initiatives.
Abstract: The purpose of this paper is to provide an update of the major improvement in terms of ramp metering design and operations in California. These updates include ramp metering policies, ramp metering development plans, ramp metering design manual, and ramp metering and system management initiatives.
TL;DR: In this paper, the authors evaluated CS&O performance for surface roughness and transverse reflection cracking and found that section age is the most significant factor affecting the deterioration of cracks.
Abstract: Crack, seat, and overlay (CS&O) is a rehabilitation technique used on jointed plain concrete pavements in California. Although CS&O is widely used, few studies have attempted to develop performance prediction models for pavements that have been rehabilitated with this technique. This study evaluated CS&O performance for surface roughness and transverse reflection cracking. Performance data for CS&O sections in three geographic regions in California were used to develop regression performance models. These models can be incorporated into the California Department of Transportation pavement management system and used to predict future performance, assist with life-cycle cost analyses, and optimize the allocation of resources. The results of a sensitivity analysis suggest that section age is the most significant factor affecting the deterioration of CS&O pavements. Secondary factors include the annual equivalent single-axle load and layer thickness ratio. Section age as an independent variable would include ...
TL;DR: In this paper, the impact of ramp metering on traffic safety has been explored in details by examining vehicular collisions near on-ramp exits within the ramp meter operating hours before and after the activation of the metering.
Abstract: Ramp metering has been widely installed in urban areas where congestion on a freeway or an expressway may occur recurrently during weekday peak periods to enhance mainline throughput and reduce system-wide delay. These operational benefits may also help reduce vehicular emissions and improve air quality in urban areas. However, the impact on traffic safety due to ramp metering hasn't been explored in details before. Supported by physical understanding and arguments, we characterize the ramp metering influence on freeway safety by examining vehicular collisions near on-ramp exits within the ramp meter operating hours before and after the activation of the ramp metering. Collisions for a sample of 19 operating ramp meters along several freeways in northern California were collected and organized to show that ramp metering can help reduce freeway collisions at the vicinity of on-ramp exits. It was found that the average reductions on freeway collisions in the vicinity of an on-ramp exit are around 36%. Altho...
TL;DR: In this article, the authors evaluated heavy-duty pavement innovations developed through research for a major rehabilitation project in California were evaluated and the performance benefits of the innovations were examined, and the economic benefits from implementation of the pavement designs were analyzed.
Abstract: Heavy-duty pavement innovations developed through research for a major rehabilitation project in California were evaluated. The performance benefits of the innovations were examined, and the economic benefits from implementation of the pavement designs were analyzed. Benefits are presented through descriptions of the rehabilitation project, background on the development of long-life pavement rehabilitation innovations, and design requirements that limit permanent deformation (rutting) within the first 5 years of service. Results from field measurements confirmed that the innovative pavements met the performance criterion. The final results of a pilot study to quantify direct benefits stemming from accelerated pavement testing are presented. Cost-benefit analysis that included agency costs with and without road user costs was used, and the influence of the discount rate in net present value calculations is given. Road user costs had a significant influence on cost-benefit calculations, especially in the ca...
03 Jul 2013
TL;DR: The Caltrans Reference Manual for Earth Retaining Structures as mentioned in this paper describes geotechnical and structural design procedures for earth retaining systems in accordance with the general principles and recommendations stipulated in AASHTO LRFD Specifications (2010).
Abstract: This report presents the "Caltrans Reference Manual for Design of Earth Retaining Structures." It describes the geotechnical and structural design procedures for earth retaining systems in accordance with the general principles and recommendations stipulated in AASHTO LRFD Specifications (2010). It corrects errors in the original edition and makes major amendments to some chapters. The formulation and the derivation of the Composite Log-Spiral Method was examined and several necessary improvements to that model were identified. The improved model, the Log- Spiral-Rankine Model, is based on a limit-equilibrium approach, and accounts for the magnitude of earthquake acceleration, the structure’s height, the backfill soil properties, and the mobilized interface friction angle between the backfill and the earth-retaining structure. Other software developed in the course of this research was used to debug Caltrans' CT-Rigid and CT-FLEX software.
TL;DR: In this paper, two safety management tools have been developed for the California Department of Transportation (Caltrans), one is the continuous risk profile (CRP) approach, which is a network screening procedure, and the other is the California Safety Analyst (CASA), a web-based application designed to assist state safety engineers in conducting safety investigations and in documenting their findings.
Abstract: Two safety management tools have recently been developed for the California Department of Transportation (Caltrans). One is the continuous risk profile (CRP) approach, which is a network screening procedure, and the other is the California Safety Analyst (CASA), a web-based application designed to assist state safety engineers in conducting safety investigations and in documenting their findings. This paper provides a qualitative description of the two tools and summarizes feedback from more than 100 Caltrans safety engineers who attended demonstrations of the web-based application. Findings from both empirical analysis and the survey indicate that CRP can significantly reduce the false positive rate and that CASA can greatly improve the efficiency of traffic safety investigations. However, misunderstandings remain about the relationship between the CRP approach, other methods explained in the Highway Safety Manual, and different safety management tools. The misunderstandings create challenges for the dep...
TL;DR: In this paper, a comprehensive list of bridge preservation actions, as identified by bridge experts, and the specific actions that the experts defined as preservation was developed with input from 12 departments of transportation (DOTs).
Abstract: There has been progressive interest from FHWA and state departments of transportation (DOTs) in considering bridge preservation an essential part of a comprehensive bridge program. The available definitions of bridge preservation give a conceptual overview; they do not identify specific bridge preservation actions. The objective of this study was to come up with a comprehensive list of bridge actions, as identified by bridge experts, and to identify the specific actions that the experts defined as preservation. A comprehensive list of 94 bridge actions was developed with input from 12 DOTs. Through an online survey, bridge experts were asked to classify each bridge action as operations, maintenance, preservation, rehabilitation, improvement, or replacement. Although the level of consensus in the final classification of the bridge actions varied, 64 actions were assigned to the same category by more than 50% of the respondents. The authors used the simple majority to determine an action's classification bu...
TL;DR: The lower limit recommended for onramp weaving length needed for a driver to merge into the freeway traffic successfully is determined based on the physical solutions derived from the paradigm and a physical constraint for avoiding potential rear-end collisions between the slow merged vehicle and the following vehicle on freeway.
Abstract: Onramp merging may be difficult if the onramp weaving/merging length is too short because a driver may find that even merging behind a neighboring large truck on the adjacent outside lane may not be completed safely. Because of insufficient weaving length for onramp acceleration, a slow merged vehicle may be rear-ended by a following vehicle on the outside lane when speed differential between the onramp vehicle and the following vehicle is relatively high. Nevertheless, short onramps at occasions are designed and built when right of way is constrained possibly by a variety of issues. The design onramp weaving length hasn't been well explained physically in various existing guidelines or design manuals. Recently, a design paradigm, where human factors, vehicle dynamics, tire-road friction, and the onramp merging scenarios are integrated into a single framework, has been developed to resolve this merging difficulty. In this paper, the lower limit recommended for onramp weaving length needed for a driver to merge into the freeway traffic successfully is determined based on the physical solutions derived from the paradigm and a physical constraint for avoiding potential rear-end collisions between the slow merged vehicle and the following vehicle on freeway. This weaving length limit sets the minimal weaving length for safer free onramp merging and guides the practitioners/designers who encounter design situations where freeway right of way at onramp is limited.
01 Nov 2013
TL;DR: A high-accuracy localization algorithm that improves the safety of roadway workers and can detect vehicles that intrude on a work zone, alert construction workers of impending danger, and notify high-mobility vehicles approaching the work zone.
Abstract: This paper describes a high-accuracy localization algorithm that improves the safety of roadway workers. The proposed system consists of a wireless sensor network (WSN) of smart cones that includes a centralized master node and several sensor nodes. The master cone maps the topology of all sensor cones placed along the periphery of a work zone, with the goal of providing decimeter location accuracy. The low-mobility smart cone network can detect vehicles that intrude on a work zone, alert construction workers of impending danger, and notify high-mobility vehicles approaching the work zone. The master cone creates a work zone topology by estimating angles and distances relative to the sensor cones using radio interferometric measurements (RIM) and received signal strength indication (RSSI) measurements. Computer simulations characterize the performance that can be achieved for realistic environment conditions.
TL;DR: By integrating driver decisions, vehicle acceleration characteristics, tire-road traction into a single analytic framework, the location upstream of an exit where an exit sign should be installed is determined for a driver to get off at the right exit successfully.
Abstract: Considering that a driver decides to exit a highway upon seeing the guide sign upstream of an exit, subsequently the driver in an inside lane or the middle lanes must move onto the outside lane prior to exiting. The concern is whether the driver can accomplish this task safely and smoothly. It is apparent that an upstream exit sign cannot be placed too close to an exit or too far beyond several exits upstream. The MUTCD recommends that the sign should be placed 1 mile and 2 miles upstream of an exit without explaining the reasons for selecting the 1 mile distance. By integrating driver decisions, vehicle acceleration characteristics, tire-road traction into a single analytic framework, the location upstream of an exit where an exit sign should be installed is determined for a driver to get off at the right exit successfully. Practitioners can easily apply these user friendly formulae and equations derived from the framework to compute the required distance ‘D’ between a highway exit and an upstream exit sign for guiding drivers to exit the highway safely. Additionally, parameters for these formulae can be adjusted to resemble various exiting scenarios.
TL;DR: In this paper, it was shown that the obstruction may govern the minimum curve radius design as long as the left shoulder is not less than 0.92 m, when the HOV lane is contiguous to the mixed-flow lanes.
Abstract: It is well-known that obstruction inside a highway horizontal curve will lead to impaired sight distance. Highway alignment design standards in terms of the minimum horizontal curve radius are specified to allow for adequate stopping sight distance at given design speeds. For a single-lane HOV facility, inside curve obstruction may occur no matter when the facility curves to the left (per travel direction) or right. A unique situation that calls for special attention is that the adjacent mixed-flow lane traffic, once queued, may become sight obstruction. Calculations indicated that such obstruction may govern the minimum curve radius design as long as the left shoulder is not less than 0.92 m, when the HOV lane is contiguous to the mixed-flow lanes. Such governance may necessitate design speed reduction, horizontal and cross-section design adjustment, or both.
TL;DR: An exact analytic framework is established to integrate driver's field view, driver's perception-reaction, lighting condition, and parking restriction at a Ped-Xing for enhancing traffic operational safety and the size of the no parking zone by the Ped- Xing is determined exactly using equations derived from this framework.
Abstract: Pedestrians at a marked but unsignalized pedestrian crossing (Ped-Xing) must be made visible to drivers in the approaching traffic at a sufficient distance away from the crossing, and this distance is needed for stopping a vehicle before the leading Ped-Xing edge to avoid a potential traffic collision. In this paper, an exact analytic framework is established to integrate driver's field view, driver's perception-reaction, lighting condition, and parking restriction at a Ped-Xing for enhancing traffic operational safety. The size of the no parking zone by the Ped-Xing is determined exactly using equations derived from this framework. Additionally, this study sheds the light on mid-block Ped-Xing installation, which should be discouraged if parking is permitted alongside a street. Furthermore, additional visibility improvement measures at the unsignalized Ped-Xings may be needed for enhancing safe traffic operations at the crossings.
19 Mar 2013