Highway Capacity Research Articles

Evaluation and improvement pedestrians characteristics for selection section of urban area

The pedestrians walking, crossing, environment and the influence of their movement with the traffic operations are the most important elements that must be taken into account in the design of roadways and intersections in the urban area. Thus the study seeks to evaluate the level of service (LOS) of sidewalks to identify the problems facing pedestrians in crossing and movements to suggest alternatives that would increase the safety, convenience, and efficiency of pedestrian’s movement within the study area, according to scientific methodology, based on the study of traffic analytical. The study has had been chosen two locations in the Baghdad capital, are Aden and Sana’a un signalized intersections. Data were collect for traffic volume and walking speed for pedestrians as well as sidewalk width. Rate of flow and effective walkway width within Peak Hour Volume ( PHV), with the aid of video technique method to cover engineering field survey and traffic, recorded data, due to workday (Monday, Tuesday, Wednesday), for the period from 20/11/2020 to30/03/2021. Data analysis was done by using the method of (highway capacity manual 2010) to determine (LOS) in the study area, rather than for roadside interview by designing a questionnaire form to identify the crosswalk users to get their opinions about the nature of the traffic facilities in the study area. The study concluded that (LOS) of pedestrians type (E&C) in Aden and Sana’a intersections respectively. The study conducted that when the excesses were eliminated from the walkway and provided buffer zones for pedestrians crossing. LOS will be increase to (B) and (C) respectively as well as the accident rate type vehicle pedestrians decrease by (20) percent, in the other hand marking and signing will be increase safety and convenience factors moreover provide appropriate time for vehicles and pedestrians crossing and movements.

Effect of side frictions on level of service of DI Panjaitan street in Cawang - East Jakarta

DI Panjaitan street has a heavy traffic congestion on the-day-of-workday especially during peak periods from 7 am to 9 am and 5 pm to 7 pm. This research aims to determine the level of service of DI Panjaitan street especially during peak hours that caused by the traffic flow and the side friction of road. The level of service was determined by using Indonesian Highway Capacity Guidance or IHCG 2014 and the most influential variable of the side friction was determined by using multiple linear regression analysis in SPSS. The research shows that DI Panjaitan street has the level F on Monday during peak hours from 7 am to 9 am and between 5 pm to 7 pm and level from C to D occurred from Tuesday to Friday. The most influential variable of the side friction was determined by equation 0.157+ 0.002 X1 + 0.001 X2 + 0.002 X3. The research shows that the park & stop vehicle, exits + enters, not motorized vehicle, strongly correlates to the value of degree saturation with a correlation coefficient (R) of 0.792.

Effect of autonomous vehicles on travel and urban characteristics

This study considers a closed core-suburb city connected by a highway. Two travel modes, namely on-demand and frequency-based autonomous vehicles (AVs), are used for commuting between the suburb and urban core. Each resident attempts to maximize his/her individual utility with consideration to environment quality by choosing a residential location, travel mode, departure time, and non-housing composite consumption good within an expenditure budget. The traffic equilibria are analytically derived for two right-of-way policies, namely (i) the two travel modes sharing the right-of-way and (ii) frequency-based AVs-priority, with consideration of the effect of AVs on travel and urban characteristics. It was found from the analytical results that at any level of AV automation, adopting the frequency-based AVs-priority policy can reduce travel cost for suburban residents while alleviating traffic congestion. Furthermore, an increase in AV automation level results in an increase in expected trip time if the highway capacity is less elastic than the value of travel time for on-demand AVs with respect to the automation level. In addition, if the environment quality depends solely on the residential density, with an increasing level of AV automation, the suburban population and the number of residents using on-demand AVs increase, the land rent in the urban core reduces, the suburb expands, and the utility for all residents increases. These findings help to provide a better understanding of the interactions between AVs, travel and urban characteristics, and serve as a valuable reference to transportation-urban planning in the era of driving automation.

ANALISIS KINERJA SIMPANG KARANGLO PASCA PEMBANGUNAN UNDERPASS KARANGLO TOL MALANG – PANDAAN

Karanglo underpass construction aims to reduce traffic congestion at the Karanglo intersection due to the addition of the Malang - Pandaan Toll Road arm. Anyhow, at the end road of Karanglo Intersection causes traffic jam and long vehicle queue. Related with that problem, so it is necessary to analyze the intersection performance, alternative improvement, and vehicle operating cost at the Karanglo intersection. The data used in this analysis are primary and secondary data. Primary data are obtained from road geometric measurements and phase and signal cycle measurements, while secondary data are obtained from the Central Statistics Agency (BPS) of Malang Regency and forecasting LHR data and side barriers. For the data processing, it uses Indonesian Highway Capacity Manual (MKJI) method 1997. Vehicle operating cost uses a handbook from Ministry of Public Works Directorate General of Highways 2005. Based on the analysis’ result, the performance of the existing intersection condition obtained delay (D) = 220.12 and the intersection service level (LOS) = E. From the analysis’ result, it is needed an alternative of intersection refinement by designing the signal phase, so that the delay (D) = 21.99 and the intersection services level (LOS) = C. The Vehicle operating cost before there was underpass for light vehicle was Rp 6.143/km. The vehicle operating cost after the underpass for light vehicle was Rp. 4.979/km.

Tradeoffs between safe/comfortable headways versus mobility-enhancing headways in an automated driving environment: preliminary insights using a driving simulator experiment

PurposeThe anticipated benefits of connected and autonomous vehicles (CAVs) include safety and mobility enhancement. Small headways between successive vehicles, on one hand, can cause increased capacity and throughput and thereby improve overall mobility. On the other hand, small headways can cause vehicle occupant discomfort and unsafety. Therefore, in a CAV environment, it is important to determine appropriate headways that offer a good balance between mobility and user safety/comfort.Design/methodology/approachIn addressing this research question, this study carried out a pilot experiment using a driving simulator equipped with a Level-3 automated driving system, to measure the threshold headways. The Method of Constant Stimuli (MCS) procedure was modified to enable the estimation of two comfort thresholds. The participants (drivers) were placed in three categories (“Cautious,” “Neutral” and “Confident”) and 250 driving tests were carried out for each category. Probit analysis was then used to estimate the threshold headways that differentiate drivers' discomfort and their intention to re-engage the driving tasks.FindingsThe results indicate that “Cautious” drivers tend to be more sensitive to the decrease in headways, and therefore exhibit greater propensity to deactivate the automated driving mode under a longer headway relative to other driver groups. Also, there seems to exist no driver discomfort when the CAV maintains headway up to 5%–9% shorter than the headways they typically adopt. Further reduction in headways tends to cause discomfort to drivers and trigger take over control maneuver.Research limitations/implicationsIn future studies, the number of observations could be increased further.Practical implicationsThe study findings can help guide specification of user-friendly headways specified in the algorithms used for CAV control, by vehicle manufacturers and technology companies. By measuring and learning from a human driver's perception, AV manufacturers can produce personalized AVs to suit the user's preferences regarding headway. Also, the identified headway thresholds could be applied by practitioners and researchers to update highway lane capacities and passenger-car-equivalents in the autonomous mobility era.Originality/valueThe study represents a pioneering effort and preliminary pilot driving simulator experiment to assess the tradeoffs between comfortable headways versus mobility-enhancing headways in an automated driving environment.

Measuring Control Delays at Signalized Intersections in Mixed Traffic Conditions

Abstract Control delay is the key performance indicator of a signalized intersection that defines the level of service. Several models have been developed in previous research work for estimating control delays, but many of them were based on homogeneous traffic conditions. In the present study, an Open Street Map (OSM) tracker mobile application was used to measure control delays from the field. A non-linear model was developed in the present study for estimating control delays in mixed traffic conditions using a MATLAB fitting tool. The field delay is compared with the developed non-linear model delay along with the Indian Highway Capacity manual (INDO HCM) and Highway Capacity Manual (HCM) models. The control delay estimated using the model developed in the present study shows a close relation with the field delay obtained using an OSM tracker when compared to that obtained using the INDO HCM and HCM models. Therefore, the OSM tracker mobile application can be used as a field control delay measuring technique.

Evaluating the impacts of autonomous cars on the capacity of freeways in Brazil using the HCM-6 PCE methodology

This paper analyses the factors that affect the impact of autonomous vehicles (AVs) on the capacity of a freeway in Brazil using an adaptation of the HCM-6 procedure for truck PCE estimation. A version of Vissim, recalibrated to represent traffic streams and AVs on Brazilian freeways, was used to simulate more than 25,000 scenarios representing combinations of traffic (e.g., AV fleets, AV platoons, percentage of AVs and of heavy goods vehicles) and road (grades and number of lanes) characteristics. AV impacts on capacity were evaluated by means of the capacity adjustment factor (CAF) and a model to estimate CAF from control variables was fitted and validated. The results indicate increases of up to 30% in capacity with 60% of platooning-capable AVs. Statistical analyses show that the fraction of AVs in the stream and the proportion of platooning-capable AVs are the factors with the greatest impact on this increase in capacity.

Determination of Passenger Car Equivalent for Heavy Vehicles in Iran in Comparison with Highway Capacity Manual 2016

Determination of Passenger Car Equivalent for Heavy Vehicles in Iran in Comparison with Highway Capacity Manual 2016

Estimation of Time-Dependent Delay Models at Actuated Traffic Signals in Duhok City

Duhok City, developed rapidly in recent years, leading to an increase in the traffic volume on its streets which are not sufficient for this increase resulting in traffic congestion. Therefore, this paper studied the delay as an important measure of effectiveness at traffic signals. The delay was measured and predicted (for saturated and under saturated conditions) to help in solving some underestimation problems by using the transportation system management (TSM) techniques. Five signalized intersections on Barzani major street in Duhok city was chosen. Vehicle delay was measured in these intersections directly from field, then it was calculated using the time-dependent equations recommended by three different official manuals, Highway Capacity Manual (HCM2000), Canadian Capacity Guide (ITE1995) and Australian Capacity Guide (ARRB1995). After that comparisons between the results of each theoretical method and the field result was made. Finally, the regression analysis technique was used to establish different relationships between the delay data obtained from the field and each of the theoretical methods to find the best applicable model to predict the vehicle delay at signalized intersections in Duhok City. It was proved that the logarithmic relationship between field and theoretical results obtained from the Canadian Capacity Guide is the best

Retraction Note to: Motorized Level of Service Classification for Urban Uncontrolled Intersections

Service and total delay are considered for classifying MLOS and intersections, respectively. GPS is used to collect travel time and speed data for turning movements that are transformed into average delay values. Thirteen junctions from eight different cities in India form the dataset. Divisive followed by agglomerative clustering (DAC-HAC) algorithm is applied as a two-step process for obtaining the service and total delay ranges. Validation of clusters is performed based on the Davies-Bouldin score, Calinski-Harabasz index, and Silhouette gaps. Based on DAC-HAC, uncontrolled intersections are classified into six categories (Cat-I, II, III, IV, V, and VI). Results indicate MLOS classes “D”, “E” and “F” have significantly higher service delay ranges as compared to Highway capacity manual “control” delay ranges indicating mixed traffic conditions. Most of the uncontrolled intersections under mixed traffic fall under Cat-IV, V, and VI, having higher total delay ranges (> 60 s/ vehicle/ approach). Finally, validation of the clustering results is done for geometric and roadside environmental features.

Intersection Signal Timing Optimisation for an Urban Street Network to Minimise Traffic Delays

The ever-increasing travel demand outpacing available transportation capacity especially in the U.S. urban areas has led to more severe traffic congestion and delays. This study proposes a methodology for intersection signal timing optimisation for an urban street network aimed to minimise intersection-related delays by dynamically adjusting green splits of signal timing plans designed for intersections in an urban street network in each hour of the day in response to varying traffic entering the intersections. Two options are considered in optimisation formulation, which are concerned with minimising vehicle delays per cycle, and minimising weighted vehicle and pedestrian delays per cycle calculated using the 2010 Highway Capacity Manual (HCM) method. The hourly vehicular traffic is derived by progressively executing a regional travel demand forecasting model that could handle interactions between signal timing plans and predicted vehicular traffic entering intersections, coupled with pedestrian crossing counts. A computational study is conducted for methodology application to the central business district (CBD) street network in Chicago, USA. Relative weights for calculating weighted vehicle and pedestrian delays, and intersection degrees of saturation are revealed to be significant factors affecting the effectiveness of network-wide signal timing optimisation. For the current study, delay reductions are maximised using a weighting split of 78/22 between vehicle and pedestrian delays.

Slugging: Casual Carpooling for Urban Transit

Problem definition: “Slugging,” or casual carpooling, refers to the commuting practice of drivers picking up passengers at designated locations and offering them a free ride in order to qualify for high-occupancy vehicle (HOV) lanes. Academic/practical relevance: It is estimated that tens of thousands of daily commuters rely on slugging to go to work in major U.S. cities. As drivers save commute time and passengers ride for free, slugging can be a promising Smart Mobility solution. However, little is known about the welfare, policy, and environmental implications of slugging. Methodology: We develop a stylized model that captures the essence of slugging. We characterize commuters’ equilibrium behavior in the model. Results: We find that slugging indeed makes commuters better off. However, the widely observed free-ride tradition is socially suboptimal. As compared with the social optimum, commuters always underslug in the free-slugging equilibrium when highway travel time is insensitive to slugging activities but may overslug otherwise. The socially optimal outcome can be achieved by allowing pecuniary exchanges between drivers and passengers. Interestingly, passengers may be better off if they pay for a ride than if they do not under free slugging. We also find that although policy initiatives to expand highway capacity or improve public transportation always increase social welfare in the absence of slugging, they may reduce social welfare in areas where free slugging is a major commuting choice. Nevertheless, these unintended consequences would be mitigated by the introduction of pecuniary exchanges. Finally, contrary to conventional wisdom, slugging as a form of carpooling can result in more cars on the road and thus, more carbon emissions. Managerial implications: Our results call upon the slugging community to rethink the free-ride practice. We also caution that slugging benefits commuters possibly to the detriment of the environment.

Modeling Bus Capacity for Bus Stops Using Queuing Theory and Diffusion Approximation

For bus service quality and line capacity, one critical influencing factor is bus stop capacity. This paper proposes a bus capacity estimation method incorporating diffusion approximation and queuing theory for individual bus stops. A concurrent queuing system between public transportation vehicles and passengers can be used to describe the scenario of a bus stop. For most of the queuing systems, the explicit distributions of basic characteristics (e.g., waiting time, queue length, and busy period) are difficult to obtain. Therefore, the diffusion approximation method was introduced to deal with this theoretical gap in this study. In this method, a continuous diffusion process was applied to estimate the discrete queuing process. The proposed model was validated using relevant data from seven bus stops. As a comparison, two common methods— Highway Capacity Manual (HCM) formula and M/M/S queuing model (i.e., Poisson arrivals, exponential distribution for bus service time, and S number of berths)—were used to estimate the capacity of the bus stop. The mean absolute percentage error (MAPE) of the diffusion approximation method is 7.12%, while the MAPEs of the HCM method and M/M/S queuing model are 16.53% and 10.23%, respectively. Therefore, the proposed model is more accurate and reliable than the others. In addition, the influences of traffic intensity, bus arrival rate, coefficient of variation of bus arrival headway, service time, coefficient of variation of service time, and the number of bus berths on the capacity of bus stops are explored by sensitivity analyses.

Congestion in highways when tolls and railroads matter: evidence from European cities

Abstract Using data from the 545 largest European cities, we study whether the expansion of their highway capacity provides a solution to the problem of traffic congestion. Our results confirm that in the long run, and in line with the ‘fundamental law of highway congestion’, the expansion in cities of lane kilometres causes an increase in vehicle traffic that does not solve urban congestion. We disentangle the increase in traffic due to the increases in coverage and in capacity. We further introduce road pricing and public transit policies in order to test whether they moderate congestion. Our findings confirm that the induced demand is considerably smaller in cities with road pricing schemes, and that congestion decreases with the expansion of public transportation.

Traffic Performance Evaluation for Selected Streets within the Southern Part of Al-Najaf City Network

Urban streets are essential parts in cities and their development can enhance various aspects of economic life and social activities. Al-Najaf city is one of the Iraqi developing cities that has been suffering from traffic congestion at various sections of its street network. The reasons, locations and intensities of these congestions are important to be regularly diagnosed for two key reasons: first, in order to choose the right traffic engineering solutions and second to adequately prioritize the funding required for planning and implementing the traffic management programs for these congested sections. This paper attempts to evaluate the performance of the main urban streets located within the southern part of Al-Najaf city street network during evening peak hours. The methodology includes collecting field data and conducting traffic surveys such as traffic volume, travel time and free flow speed surveys. The evaluating approaches illustrated in the U.S Highway Capacity Manual are adopted as a tool for assessing the operational performance for the selected urban streets. The results reveal that there are several segments that operate at their capacity (LOS E) or even under congested flow condition (LOS F). The analysis also shows that whereas some segments are with good LOS using volume-capacity ratio (v/c) criterion, they are actually with low LOS based on field observations or when using travel time as a performance measure. This indicates the inadequacy of using v/c ratio alone in evaluating urban streets because part of the congestion at such streets is due to side friction operational delays rather than over traffic demand.

Analysis of highway performance under mixed connected and regular vehicle environment

Purpose This study aims to study the connected vehicle (CV) impact on highway operational performance under a mixed CV and regular vehicle (RV) environment. Design/methodology/approach The authors implemented a mixed traffic flow model, along with a CV speed control model, in the simulation environment. According to the different traffic characteristics between CVs and RVs, this research first analyzed how the operation of CVs can affect highway capacity under both one-lane and multi-lane cases. A hypothesis was then made that there shall exist a critical CV penetration rate that can significantly show the benefit of CV to the overall traffic. To prove this concept, this study simulated the mixed traffic pattern under various conditions. Findings The results of this research revealed that performing optimal speed control to CVs will concurrently benefit RVs by improving highway capacity. Furthermore, a critical CV penetration rate should exist at a specified traffic demand level, which can significantly reduce the speed difference between RVs and CVs. The results offer effective insight to understand the potential impacts of different CV penetration rates on highway operation performance. Originality/value This approach assumes that there shall exist a critical CV penetration rate that can maximize the benefits of CV implementations. CV penetration rate (the proportion of CVs in mixed traffic) is the key factor affecting the impacts of CV on freeway operational performance. The evaluation criteria for freeway operational performance are using average travel time under different given traffic demand patterns.

Bicycle Level of Service: Proposed Updated Pavement Quality Index

The Highway Capacity Manual (HCM) employs a simple five-point system to assess the quality of bikeway pavement as part of the comprehensive bicycle level of service (LOS) evaluation. Unfortunately, the ambiguous and rudimentary nature of the existing HCM Pavement Quality Index (PQI) fails to offer an objective review of bikeways across different jurisdictions. In the following analysis, first is an assessment of the PQI and bicycle LOS in the HCM. To demonstrate the impact of the pavement quality rating and the importance of a more standardized evaluation method, a sensitivity analysis is performed. An improved PQI matrix is then proposed based on a comprehensive literature synthesis. The new matrix allows for a more holistic understanding of pavement quality in a three-category framework. The proposed methodology includes specifications for the functionality, structural integrity, and maintenance of bikeways. Within each category, objective thresholds are defined, such as for potholes, cracks, and maintenance routines, to minimize any potential subjectivity.

Validating and Calibrating the Highway Capacity Manual Arterial Travel Time Reliability Methodology

The 6th edition of the Highway Capacity Manual (HCM6) introduced a methodology for estimating and forecasting arterial travel time (TT) distributions (TTD) and their associated travel time reliability (TTR) metrics. Recently, it was shown that the HCM6 severely underestimated both the TTD and the TTR metrics for a test network in Lincoln, NE, U.S. Subsequently, it was shown that the underestimation issue could be eliminated through a proposed calibration methodology. Because this validation and calibration work was done on a single, relatively short section of arterial roadway there is an open research question on whether this finding applies to longer and more congested arterial roadways. The goal of this paper is to validate and calibrate the HCM6 TTR methodology on five arterial roadway testbeds that are longer and more congested than the original testbed. Empirical data from the National Performance Management Research Data Set (NPMRDS) which is managed by INRIX was used to represent the ground truth. Similar to the original study, it was found that the HCM6 TTR methodology severely underestimated the TTDs, and their respective TTR metrics, on all five testbeds. This is problematic, because the HCM6 methodology indicates that the corridors had more reliable TT than the empirical data would suggest. It was also shown that the calibration methodology eliminated this underestimation. It is recommended that users of the HCM6 TTR methodology validate and, if necessary, calibrate the model using local empirical travel data.

Queue Analysis at Work Zones from Field-Collected Data

Estimation of the capacity of work zones is vital to manage the possibility of traffic flows exceeding capacity and resulting in unbearable queues during work zone lane closures. A plethora of research papers have studied several ways to estimate work zone capacity, with the Highway Capacity Manual (HCM) having its own methodology to estimate capacity based on various site characteristics. However, HCM always recommends validating its model with local data to reflect the actual driving behavior of the region. This study considered work zone capacity as a function of queue discharge rate (QDR), defined as the 15-min average flow rate immediately after breakdown, also known as postbreakdown flow rate. By collecting data from 10 different work zones within the state of Louisiana, the study estimated QDR and its corresponding duration at breakdowns. An average QDR of 1,664 pcphpl and an associated queue of 120 min average duration was found. Analysis of variance showed that average QDRs across all sites were not significantly different. The QDR prediction model revealed that a closed right lane and a work zone on linear roadways significantly increased the discharge rate. However, the presence of nearby exit ramps, daytime scenarios, and an increase in the speed ratio and truck percentages were found to decrease the discharge rate. A separate model for the duration of queue or breakdown found the time of day, change in the speed ratio, presence of entry ramp, location of work zones, and annual average daily traffic of the roadway to be significant variables.

Multilane Microscopic Modeling to Measure Mobility and Safety Consequences of Mixed Traffic in Freeway Weaving Sections

Weaving sections are components of highway networks that introduce a heightened likelihood for bottlenecks and collisions. Automated vehicle technology could address this as it holds considerable promise for transportation mobility and safety improvements. However, the implications of combining automated vehicles (AuVs) with traditional human-driven vehicles (HuVs) in weaving freeway sections have not been quantitatively measured. To address this gap, this paper objectively experimented with bidirectional (i.e., longitudinal and lateral) motion dynamics in a microscopic modeling framework to measure the mobility and safety implications for mixed traffic movement in a freeway weaving section. Our research begins by establishing a multilane microscopic model for studied vehicle types (i.e., AuV and HuV) from model predictive control with the provision to form a CACC platoon of AuV vehicles. The proposed modeling framework was tested first with HuV only on a two-lane weaving section and validated using standardized macroscopic parameters from the Highway Capacity Manual. This model was then applied to incrementally expand the AuV share for varying inflow rates of traffic. Simulation results showed that the maximum flow rate through the weaving section was attained at a 65% AuV share. At the same time, steadiness in the average speed of traffic was experienced with increasing AuV share. The results also revealed that a 95% AuV share could reduce potential conflicts by 94.28%. Finally, the results of simulated scenarios were consolidated and scaled to report expected mobility and safety outcomes from the prevailing traffic state and the optimal AuV share for the current inflow rate in weaving sections.