Impact of Heavy Vehicles on Freeway Operating Characteristics under Congested Conditions

Ahmed, Umama; Drakopoulos, Alexander; Ng, ManWo

doi:10.3141/2396-04

Cited by 9 publications

(5 citation statements)

References 4 publications

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“…The distinctly longer headways the drivers of heavy semitrailer trucks kept from PCs compared with the short headways kept by their peers driving small semitrailer trucks. A possible explanation may be found in vehicle weights [39.6 kips, Class 8; 59.2 kips, Class 9 in a study referenced in Ahmed et al (26)]: longer headways related to heavier vehicle-braking distances.…”

Section: Discussionmentioning

confidence: 99%

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Field-Derived Freeway Passenger Car Equivalents for Congested Conditions

Drakopoulos

Dehman

2015

Transportation Research Record

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Heavy-vehicle (HV) impact on freeway operations in the Highway Capacity Manual 2010 is evaluated on the basis of values for passenger car equivalents (PCE) for buses–trucks and recreational vehicles. These values were calibrated for relatively uncongested freeway conditions [Levels of Service (LOS) A through C] because inadequate field data on HV behavior under congested conditions were available; furthermore, field-collected headway information was based on the average headway for vehicles in a particular class, regardless of the type of vehicle that they were following. The goal of this paper was to collect and analyze freeway field data on HV headways with an emphasis on lower speeds typically associated with an LOS E (capacity) or F (forced-flow conditions). The effect that a leading vehicle has on headways was captured and analyzed for 10 leading–following vehicle pair types containing at least one passenger car (for example, buses followed by passenger cars). Headway statistics were analyzed for nine speed ranges (up to 20 mph, 20 to 25 mph, 25 to 30 mph, 30 to 35 mph, 35 to 40 mph, 40 to 45 mph, 45 to 50 mph, 50 to 55 mph, and over 55 mph) and 10 vehicle pair types. Values for PCEs were derived for each speed range on the basis of average headway for a specific vehicle pair type divided by the average headway between passenger cars. Leading and following vehicle classes and speeds were found to have a significant influence on headways and values for PCEs.

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Section: Discussionmentioning

confidence: 99%

“…Vehicles were classified into three types by using the FHWA scheme of 13 vehicle classes (Table 1): motorcycles (Class 1), passenger cars (PC = Classes 2 and 3), light trucks (LT = Classes 4 to 7), and heavy trucks (HT = Classes 8 to 13). Average headways for (26).…”

Section: Freeway Pce Valuesmentioning

confidence: 99%

Field-Derived Freeway Passenger Car Equivalents for Congested Conditions

Drakopoulos

Dehman

2015

Transportation Research Record

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“…Heavy vehicles are known to have an impact on the traffic stream. Ahmed, Drakopoulos, and Ng (2013) found that headways between passenger cars increased due to the presence of heavy vehicles. They also found that the maximum throughput of the freeway decreased when the heavy vehicle percentage increased by more than 3 percent.…”

Section: Merging Freeway Designs and Their Safetymentioning

confidence: 99%

Standard freeway merge designs support safer driver behaviour compared to taper designs: a driving simulator study

et al. 2020

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Standard freeway merge designs support safer driver behaviour compared to taper designs: A driving simulator studyRoad geometric design standards provide various possibilities for merging freeways with a decreasing number of lanes. In this study, an alternative design (i.e. taper design) is investigated and compared with the standard design under three different heavy vehicle compositions to understand driving performance in relation to the flow of traffic. Taper design is not always the first choice in the road geometric design guidelines and the designer has to provide arguments for selecting this design. Taper design and its comparison with other alternatives are also not well explored in literature. In this study, a driving simulator was used to examine and compare the performance of these two designs under different heavy vehicle compositions. Qualitative results showed that the perceived safety was better for the standard design compared to the taper design. Mean speed, acceleration, standard deviation of acceleration/deceleration, and cumulative lane changes were chosen as behavioural parameters to compare these two designs using MANOVA and repeated measures ANOVA. Results revealed that drivers' discomfort in performing merging manoeuvres was greatest in case of a taper design and when the percentage of heavy vehicles was moderate (15%). Overall, the standard design was found to be more favourable.

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“…The other category of vehicles was the passenger car, which dominated the traffic stream. Ahmed et al (2013) conducted a study to determine the impact of Heavy Vehicles (HVs) on performance at different congestion levels. The study findings reveal that with an increase in the HVs percentage, the capacity and Level of Service (LoS) deteriorated.…”

Section: Introductionmentioning

confidence: 99%

Effect of Mixed Traffic Platooning by Commercial Vehicle Types on Traffic Flow Characteristics of Highways

Singh

Rajesh

Santhakumar

2022

Period. Polytech. Transp. Eng.

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The existence of different types of Commercial Vehicles (CVs) in the shared roadway affects traffic flow characteristics differently from other vehicles. Owing to the uncertain placement and movement of these CVs in both longitudinal and lateral directions, the opportunities for lane changing and overtaking by other vehicles with lower maneuverability decrease, resulting in the formation of platoons. The study's primary aim is to assess the effect of mixed traffic platoons formed by three different classes of CVs on highway traffic speed, flow, and density under two different traffic regimes (regimes A and B). In this study, regime A represents the non-platooning condition, and regime B represents the platooning condition. Bi-directional traffic data was collected from the highway sections in India using an Infra-Red sensor-based device. The critical leading time headway is determined for the different CVs (platoon leaders) based on the mean absolute relative speed of platoons. The speed-flow-density plots are established using the macroscopic fundamental diagrams for the highway sections under regimes A and B to quantify the platooning impacts of CVs on the traffic characteristics. The study findings reveal that the speed at capacity, density at capacity, and traffic capacity decreased significantly due to CVs' influence on the general traffic mix during the mixed traffic platooning conditions. However, this effect was found to be relatively higher during the Heavy Commercial Vehicle operation as a platoon leader compared to Medium Commercial Vehicle and Light Commercial Vehicle as a platoon leader.

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Impact of Heavy Vehicles on Freeway Operating Characteristics under Congested Conditions

Cited by 9 publications

References 4 publications

Field-Derived Freeway Passenger Car Equivalents for Congested Conditions

Field-Derived Freeway Passenger Car Equivalents for Congested Conditions

Standard freeway merge designs support safer driver behaviour compared to taper designs: a driving simulator study

Effect of Mixed Traffic Platooning by Commercial Vehicle Types on Traffic Flow Characteristics of Highways

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