Road Geometric Design Research Articles

Selective State DOT Lane Width Standards and Guidelines to Reduce Speeds and Improve Safety

This research investigates the lane width standards and guidelines implemented by various State Departments of Transportation (DOTs) to reduce vehicle speeds and enhance road safety. Lane width reduction is often perceived as a strategy to mitigate speed and improve safety. Still, its effectiveness and implications vary across different contexts, including regions, urban/rural settings, or other geometric design features. Drawing from interviews with five State DOTs and a review of their road design manuals, this study aims to identify suggested lane widths depending on the contexts, design exception process when narrowing or widening lane widths, and introduce representative before/after studies. The findings indicate that State DOTs tend to have lower recommended lane widths in urban areas than in rural areas. Moreover, lane width standards among these states vary due to several factors, including the geographical location of roadways (urban or rural areas), design or posted speeds, traffic volume, road classification, and geometric road design features. Design exceptions are required if the existing or proposed design element is incompatible with both AASHTO and department governing criteria. In conclusion, the findings will provide valuable insights and recommendations for policymakers, transportation planners, and road engineers to inform optimal lane width and decision-making processes.

Integrating building information modelling (BIM) and extended reality (XR) in the transportation infrastructure industry

Although building information modelling (BIM) has been widely used in the building industry, its usage in infrastructure projects such as bridges has been very challenging. Extended Reality (XR) that simulates a construction project is still considered a new technology in the Architecture, Engineering, and Construction (AEC) industry. This paper investigates the viability of integrating both BIM and XR technologies into transportation infrastructure projects. A fully integrated workflow for introducing different XR, Augmented Reality (AR), and Virtual Reality (VR), and BIM technologies using different software for a case study of El-Merghani bridge, a reinforced concrete girder type bridge, was developed. The models for the bridge included GIS integration and geometric road design according to AASHTO, documentation, shop drawings and quantification were developed for the bridge. A hypothetical time schedule was generated in Oracle Primavera P6 elevating the BIM model to 4-D and developing VR and AR virtual experiences with the capability to investigate, visualize, and present the model in a virtual environment, at a high level of immersion. Additionally, the associated risk reduction for the considered XR technology was assessed using Monte Carlo simulation. The workflow and the detailed 3D models developed for the bridge along with the highly immersive VR and AR experiences have provided an interactive platform for engineers and different stakeholders to monitor the project during the design and construction phases. The risk analysis showed that significant cost savings can be achieved with the utilization of VR and AR technology in bridges construction.

Analysis of the Duration of Mandatory Lane Changes for Heavy-Duty Trucks at Interchanges

Due to the different driving characteristics of different vehicle models, inappropriate mandatory lane changes (MLCs) by heavy vehicles at interchanges often lead to serious traffic accidents. Therefore, this paper focuses on the impact of road geometric design on the MLC duration of heavy trucks by using full time-domain trajectory data. Specifically, we use the generalized additive time-varying Cox model to establish the MLC duration model of heavy trucks at interchanges, then analyze the combined influence of geometric elements. The results show that the consistency index of the model is 0.9, indicating that it has advantages in building models in complex environments. The length of the deceleration lane, ramp type, and curve radius have a significant impact on the validity and duration of MLCs. This finding provides a theoretical and methodological reference for the safety analysis of interchange areas and the refinement of road geometric design.

Potential Impacts of Connected and Autonomous Vehicles on Controlling Criteria for Road Geometric Design: A Review

The development of connected and autonomous vehicles (CAVs) has progressed rapidly with advancements in intelligent transportation systems, automated driving technologies, and regulatory reforms worldwide. As the efficiency and safety of surface transportation heavily rely on highway geometric design, understanding the impact of CAVs on design control elements is essential to fully capitalize the benefits CAVs may offer. The objective of this study is to conduct a comprehensive review of existing literature to synthesize how CAVs can influence the controlling criteria for highway geometric design. Over 30 articles were thoroughly reviewed to gain insights into the impacts of CAVs on highway design and potential explanations for them. As CAVs could potentially reduce the minimum required stopping sight distance, they create opportunities to decrease other geometric dimensions, such as horizontal curve radius, length of vertical curves, horizontal sight offset, extra widening, and so on. However, this optimization is more feasible in an environment with fewer human-driven vehicles. Moreover, further related research needs to be done in mixed traffic streams and complex driving conditions. The critical discussions of this study can offer valuable insights, shedding light on the potential benefits and implications that an automated transportation sector may bring to future road geometry design.

Geometric Evaluation of Road Construction on The Ir Sutami PJR Climb Bandar Lampung Using Topographic Measurements

In general, steep inclines are made winding for the reason that they reduce the energy required to reach the same height. The slope of the incline will be gentler with curves so it is easier to climb, because the car does not have enough power to climb steep slopes so the road is made winding. Based on accident data from the KNKT, the highest number of accidents that occurred on the PJR Bandar Lampung ramp was 21 incidents in a year. Geometric road on an incline. The winding and narrow condition of PJR Bandar Lampung makes it difficult for vehicles to pass this section of road. The aim of this research is to carry out geometric analysis and evaluation of roads on the PJR Bandar Lampung incline based on Road Geometric Design Guidelines Number 13/P/BM/2021 using topographic measurements. The results of the geometric evaluation of the road were suitable for corner 4 with a superelevation below 6% and with a minimum radius from a speed of 20 km/h to 50 km/h, while the results were not suitable for the average ideal lane width of 3 m. maximum superelevation is 10.01%, maximum slope is 9.81% and critical slope length is 9.33%. So the road geometry does not comply with Road Geometric Design Guidelines Number 13/P/BM/2021.

Analisis Hubungan Geometrik Jalan dengan Potensi Kecelakaan di Jalan Imogiri - Dlingo, Bantul, Indonesia

Imogiri - Dlingo road section is a primary collector road located in the Mangunan tourist area, Bantul, Indonesia. This road is a provincial road with hilly terrain, lots of sharp turns, and long ascents and descents, which are potential for traffic accidents. Police data records that in February 2022 there was an accident on this road with 13 deaths and 33 injuries. Therefore, this study aims to evaluate road geometric, both horizontal and vertical alignments on Imogiri - Dlingo road based on Guidelines for Road Geometric Design number 13/P/BM /2021. To do so, road geometric analysis is conducted by employing road safety inspection data, which is then modeled using AutoCAD Civil 3D software. Based on the survey on road geometric, it is known that the number and width of lanes and shoulders are in accordance with Guidelines. Meanwhile, the analysis results using computer program show that this road has 24 horizontal and 6 vertical alignments. Nevertheless, 87% of bend radius, 67% of curve length, 58% of bend angle, 43% of slope, 57% of critical length, and 67% of control design (K) are not fulfilled the requirements. Therefore, Imogiri - Dlingo road is dangerous road and is potentially causing fatal accidents.

Research on traffic accident prediction of expressway tunnel based on B-NB model

Objective The study investigates the relationship between traffic accidents in expressway tunnels and their influencing factors, with the aim of predicting traffic accidents within tunnels and presenting reasonable recommendations to improve tunnel safety. Methods The study utilizes a dataset of 586 traffic accidents occurring exclusively within 8 tunnels along a Guangdong Province expressway from 2017 to 2021. It applies the geometric alignment consistency principle to segment road sections, defines tunnel boundaries based on driving behavior, and employs a Bayesian-modified negative binomial regression model (B-NB model) to identify 6 significant variables from a pool of 17 factors. Results The predictive performance of the B-NB model demonstrated similarities to that of the fixed parametric model. This outcome might be attributed to the chosen prior distribution settings and the limited amount of data. Nonetheless, the model effectively captures relationships among variables, leading to improved accuracy in accident prediction and the predictive model achieves a 76.1% accuracy rate. Conclusions Drawing from the estimation results, practical measures are suggested across three dimensions: road geometric alignment design, tunnel traffic safety facilities, and traffic emergency management. These proposals aim to ameliorate the severe consequences of tunnel accidents. Future research will explore an in-depth comparison of estimation results, considering the impact of time and variable correlation on the prediction model by expanding the existing data. This will guide the direction of subsequent research endeavors.

MODEL REGRESI LINIER PENGARUH STANDAR TEKNIS JALAN TERHADAP KECELAKAAN LALU LINTAS PADA JALAN PROVINSI (STUDI KASUS : RUAS JALAN PEMALANG – PURBALINGGA)

In the 2016-2021, there were 12 accidents with 22 deaths and 107 injuries on the Pemalang – Purbalingga road section. One of the factors causing accidents is the lack of attention to infrastructure that meets safety aspects. Even though the number of accidents caused by infrastructure is relatively small when compared to the human error (human) and vehicle (facility) factors, serious attention must still be paid. Traffic accidents caused by a lack of road infrastructure are generally caused by an inaccurate road geometric design, poor road surface conditions, lack of visibility and so on. Therefore the research aims to find accident-prone locations, the causes of accidents from the standard values of road technical requirements and accident regression models. The results of this study. Segments that are categorized as accident-prone locations are STA 32+000, 34+000, 36+000, 47+000 and 48+000. Substandard grades will be the cause of traffic accidents based on road technical requirements. The regression model that can be used to predict the number of accidents on provincial roads according to the variables examined in this study is: Y = -2.618 + 0.049 Grade – 0.019 X Slope – 0.008 H Curv – 0.417 V Curv + 0.264 road width + 0.081 condition IRI roads + 0.014 PCI Road Conditions

Traffic microsimulation for road safety assessments of vehicle automation scenarios: Model comparison and sensitivity analysis

The possible implementation of Automated Vehicles (AVs) in the traffic flow implies that future safety conditions should be assessed by considering promiscuous traffic scenarios (composed of traditional vehicles and AVs). However, real safety performance data related to AVs are still scarce and unreliable. Thus, road safety assessments of future scenarios should necessarily be based on traffic simulations and surrogate safety measures (i.e., related to traffic conflicts, which are different from observed crashes). In the context of traffic simulation, the first step consists in assessing the currently available traffic models to match their characteristics with the possibility of reliably simulating AVs and their behavior in traffic, according to the specific variables of the investigated site (i.e., road type, road geometric design, number of intersections). After the model selection stage, a sensitivity analysis is necessary to identify the most crucial model parameters and their influence on the simulation output, with particular regard to those affecting safety performances. The sensitivity analysis paves the way for making traffic modelers aware of the effects of possible modifications to the simulation parameters in case of AV scenarios. In this research, this procedure was tested on a two-way two-lane rural road network. Among the analyzed traffic models, the Gipps model was highlighted as the most suitable to account for AVs in this specific context. The sensitivity analysis revealed that the most influencing parameters of the Gipps model in the context of safety assessments are: clearance, safety margin factor and sensitivity factor, which were revealed to be greatly influential on all types of traffic conflicts. Two other control tests with different simulated vehicle types were run to highlight the stability of the results coming from the sensitivity analysis in other scenarios.

Case study of superelevation design at an expressway interchange by using ADSCivil Road software

Superelevation is known as a transverse slope made available to mitigate the impact of centrifugal force and minimize the vehicle’s tendency to overturn and skid. However, in an intersection or interchange that has horizontal curves with small radius consecutively, it is difficult to design superelevation. If the superelevation arrangement is not good enough, the alignment is not smooth, causing unfavourable and unsafe conditions. Moreover, for expressway interchange, it become more complicated to design by manual method because the expressway requirements in term of safety and aesthetics is higher than that of conventional intersection. On the other hand, ADSCivil Road, a software in the ADSCivil solution suite for infrastructure design developed by Baezeni Soft Co, Ltd. is a useful tool for geometric road design. This paper presents the results of ADSCivil Road software application in designing the superelevation at the expressway. ADSCivil Road has arranged superelevation for an interchange ramp (with a design speed of 60 km/h) that includes the small radius circular curves connecting together (R=125 m and R=100 m). The results show that using the superelevation diagram and corridor model in ADSCivil Road makes the superelevation design process more intuitive, make it easier to adjust the slope at each point, and controls the rate of superelevation difference. In addition, ADSCivil Road automatically updates the superelevation change for profile, cross-section and plan. Also, 3D simulation results show that the superelevation layout for this interchange meets technical, economic, and aesthetic requirements. Obviously, it can be seen that can become an effective tool to help engineers solve complex problems in road design.

Using convex hulls with octree/voxel representations of point clouds to assess road and roadside geometric design for automated vehicles

This paper aims to quantitatively assess the geometric design of road and roadside infrastructure for Autonomous Vehicles (AVs) using point cloud data while addressing the limitations and recommendations of previous studies. This research utilizes an ultra-dense point cloud to represent a digital twin of existing roads and simulates a set of AV sensors and phantom targets on both the road and roadside areas within this environment. A quadratic surface model, convex polyhedra/hulls with an octree/voxel data structure, a semantic segmentation variant of PointNet++, and YCbCr colour spaces were used by us to map road/roadside design readiness measures. Using the developed method, several case studies are presented to identify locations with substandard design conditions for AVs. This work can help infrastructure operators, and AV professionals make data-driven decisions regarding smart physical and digital infrastructure investments.

Crash Frequency Minimization with Severity Mitigation in Road Geometric Design Using Chance Constraint Programming Optimization

Crash frequency and crash severity are two major aspects of transportation safety. In this paper, we propose a decision-making scheme combining statistical analysis and optimization modeling to be used in transportation safety study. We conduct a safety analysis, a travel speed analysis, and an optimization analysis to develop a two-stage decision scheme to minimize crash frequency while mitigating crash severity, using data collected in urban environments in Lincoln, Nebraska. In the safety analysis and the travel speed analysis, we study the impact of lane width and other related road geometric design parameters on annual crash frequency and vehicle travel speed using count models and linear regression models, respectively. In the optimization analysis, the proposed two-stage stochastic programming model determines the lane width and other road geometric design parameters in the first stage, and then the posted road speed limit in the second stage for each scenario. To mitigate crash severity, we use a chance constraint to restrict a certain percentile of the vehicle travel speed to comply with the posted road speed limit. This two-stage decision scheme is shown to be effective for the data collected in Lincoln, Nebraska, when restricting the vehicle travel speed of up to two positive standard deviations from the mean travel speed to be under the posted speed limit. The application of a stochastic programming model that utilizes regression analysis results serves as an innovative decision scheme that effectively connects statistical analysis and optimization studies in road geometric design for transportation safety. Its objective is to minimize crash frequency while simultaneously mitigating crash severity. This methodology has extensive potential for application in various environments to assist in the reduction of both crash frequency and crash severity.

Improving geometric road design through a virtual reality visualization technique

Traffic accidents could often be avoided with more in-depth studies of traffic and the geometric layout, using, for example, driving simulators to simulate traffic conditions. The objective of this study is to qualitatively evaluate three types of visualization techniques for examining a road project (one in a 2D printed project and the others using a driving simulator in a virtual immersion system and screen visualization). The results were evaluated by the Analytic Hierarchy Process-AHP method, used to establish different weights for the analyzed variables. For this, a questionnaire was applied to undergraduate students in Civil Engineering to compare the techniques. The results show that the immersive simulation visualization has sufficient quality and can contribute to the validation of geometric designs.

“I did not see that coming”: A latent variable structural equation model for understanding the effect of road predictability on crashes along horizontal curves

Driver anticipation plays a crucial role in crashes along horizontal curves. Anticipation is related to road predictability and can be influenced by roadway geometric design. Therefore, it is essential to understand which geometric design elements can influence anticipation and cause the road to be (un)predictable. This exercise, however, is not straightforward because anticipation is individual-specific whereas road geometric design is location-specific; anticipation is latent and measuring it may not be trivial; anticipation may have several stages from the preceding tangent until the midst of the curve; and not all drivers anticipate in the same way and thus there may well be unobserved heterogeneity in the effect of anticipation on crash risk.Despite methodological advancements in crash risk modelling, there is no econometric model that can adequately explain the above complexities. This study aims to fill this gap by developing an econometric model with a new latent variable, named ‘predictability’ that is measured by individual-specific driving behaviour indicators and predicted by location-specific road geometric factors. The model is specified with random parameters to account for unobserved heterogeneity and is empirically tested by a unique dataset including detailed geometric design and driver behaviour data obtained for 156 curves in the Netherlands. Results indicate that higher exposure and uphill vertical grade are associated with increased likelihood of vehicle crashes along horizontal curves, whereas adequate superelevation and higher predictability are associated with decreased likelihood of those crashes. Pavement friction influences this likelihood too but it has varied effects. Road predictability is influenced by the differences in angle of horizontal curves, vertical grades, and width of consecutive road segments.

Safety evaluation of horizontal curves on two lane rural highways using machine learning algorithms: A priority-based study for sight distance improvements

Objective Current Road geometric design processes disregard stochastic aspects, resulting in inadequate traffic safety considerations. In addition, the primary sources of crash data are obtained from police department, insurance agency and hospitals, where detailed investigation is not carried out from a transportation perspective. So, the data obtained from these sources may or may not be reliable. The main objective of this study is to account uncertainties using reliability as a tool that considers slow down the vehicle while they maneuver the curve and to develop thresholds of reliability index associated with sight distance based on operating speed design consistent measure as a surrogate safety measure rather than using crash data. Methodology This study proposes a thresholds of reliability index associated with sight distance for various operating speed ranges based on design consistent measure. In addition, established the relationship between the consistency levels, geometric characteristics and vehicle characteristics. In this study, classical topography survey was carried out on the field using total station. The data collected comprises speed data and geometric data of 18 horizontal curves (Lane based analysis was carried out). A total of 3042 free flowing vehicle speeds have been extracted from the video graphic survey and used in the analysis. Results The threshold values of reliability indices associated with sight distance is higher as the operating speed increases for the section to be a consistent design section. The results from the Binary Logit Model show that the consistency level is significantly affected by deflection angle and operating speed. Deflection angle was negatively correlated with the in-consistency level, and the operating speed was positively correlated with in-consistency level. Conclusions From Binary Logit Model (BLM) results, we can conclude that an increase in the value of deflection angle will significantly decrease the probability of In-Consistent level, which indicates uncertainties that cause drivers to change the path of vehicle or rate of deceleration of the vehicle while maneuvering the curve will be decreased. Whereas, increase in the operating speed will significantly increase the probability of In-Consistency level.

Errata: Performance Margin for Geometric Road Design

Errata: Performance Margin for Geometric Road Design

The Geometric Design of Horizontal Curved on Jalan Drono – Nganom, Wonogiri Using Autocad® Civil 3D

An efficient network of highway infrastructure is a decisive factor in promoting the socio-economic development of a region. Road construction is intended to connect isolated areas and promote economic growth through good population mobility considering comfort, safety, and smoothness by keeping abreast of transportation technology developments. They were planning the geometric design of the highway through the process of selecting the appropriate geometric aspects as well as design controls that govern the critical elements of the highway design. The current trend of planning for geometric road design is directed at using computer programs to make the results more precise and save time and effort. In this geometric planning, the author plans a geometric horizontal curved road on the Jalan Drono - Nganom, Ngadirojo District, Wonogiri Regency, using AutoCAD Civil 3D®. The creation of this road aims to facilitate the flow of transportation and economic equality of the area with two SCS (Spiral–Circle–Spiral) type bends, a radius of 400 m, a plan speed (Vr) of 80 km/h, a maximum slope of 0.06 and a friction coefficient of 0.14.

The Geometric Design of Horizontal Alignment: A Case of Bojonggede-Kemang Area Route, West Java Indonesia

Roads are one of the basic infrastructure facilities in the development of an area. With the construction of roads, they can be used as access to transportation and as a driving force for an area's economy to grow better. The purpose of geometric planning on the Bojonggede-Kemang section road at STA 0 + 000 - STA 1 + 200 is to obtain a design that prioritizes user safety and comfort. The method used in this study is a manual method that refers to the 2021 Road Geometric Design Guidelines (PDGJ). The data used in this study used Google Earth. The results of the study obtained a class III primary local type road. The plan speed of 60 km / h was obtained based on the criteria design. Then, using values, the horizontal alignment of the Bojonggede-Kemang road section is of type S-C-S..

The Alignment Horizontal Design of Alternative Road: A Case of Jalan Subang – Cikamurang, West Java

Horizontal alignment belongs to the aspect of the geometric design of the road. Jalan Subang - Cikamurang, located in Indramayu, West Java, is planned to have three horizontal alignments. This design aims to connect Subang and Cikamurang to shorten the travel time for the surrounding community's needs. This research uses the Bina Marga method, referring to the 2021 Road Geometric Design Guidelines. First, road traffic data is obtained from the google earth application and then processed with a manual method to determine the coordinates of the road traffic and the location of horizontal alignment. Then the data obtained is processed by referring to the Bina Marga method to design horizontal alignment. Jalan Subang - Cikamurang is a Primary Local Road (Arterial Road), Primary Collector, and class III C road type. Three horizontal alignments with Spiral-Circle-Spiral (SCS) type, the first horizontal alignment is at STA 0+544.018 – 0+819.445, the second horizontal alignment is at STA 1+224.778 – 1+474.695, and the third horizontal alignment is at STA 1+763 – 2+164.390.

Vehicles lateral acceleration and speed profiles investigation at the entry area of interchange ramps as a criterion of geometric road design

The subject of road safety is the main subject of many research programs regarding the road network infrastructure. In the present study, lateral acceleration is recorded through modern instruments, depending on passing speed for each participant driver, for four (4) interchanges and six (6) horizontal curves in total. Essentially, this study emphasizes on how the geometric roads design affects driving behavior. The main purpose is to determine the effect of on-ramp applied speed and curve geometry on lateral acceleration and to create a clear speed profile of drivers during their passage from an interchange ramp. The data collection took place in morning weekend hours, in order to avoid high traffic flows and record the vehicles motions in free flow conditions. As a result, the analysis can examine the main human factors, which affect the driving behavior, too. The selected interchange ramps are mainly trumpets, but also clover and diamond sections and the under-investigation curve radii varies between 28 and 175 meters.For each curve, the presented figures correlate the speed within the curve and the lateral acceleration, while comparisons are made between the lateral acceleration recorded in this research and the literature and guidelines limits. Additionally, V85, V50 and V15 are calculated from the total measurements, taking also into account the data from three additional horizontal curves of Schistos-Skaramagas interchange investigated one year earlier. Therefore, aggregate speed profiles are created and presented.In conclusion, the results show that an increase in the speed leads to an increase in the lateral acceleration as well. Also the limit values of lateral acceleration received by drivers into smaller-radii curves, significantly exceed the maximum driver comfort limit and the maximum driver safety limit, as well as the provided -by design guidelines- values, in contrast to larger-radii curves. Regarding the speed within the curve in respect to the horizontal radius, it was found that as the radius of the curve increases the applied speed also increases. However, this increase is more abrupt for the smaller radius curves compared to the larger ones. Moreover, de Jong's models include higher values than the measurements made in the present study and much more than those presented by Jafarov's and Zaluga's model (2020), especially in cases of large horizontal radii.