Highway Curves Research Articles

3D HIGHWAY CURVE RECONSTRUCTION FROM MOBILE LASER SCANNING POINT CLOUDS THROUGH DEEP REINFORCEMENT LEARNING

Abstract. Reconstructing the geometric curves of highways holds significant value for various tasks, such as highway design, traffic simulation, and road network planning. An essential step in highway curve reconstruction is fitting highway curve models to the extracted road markings from laser scanning point clouds. Existing methods for highway curve fitting typically handle one curve at a time. However, a stretch of highway often contains multiple curves. In this paper, we introduce a novel method capable of fitting multiple highway curves simultaneously. The method leverages a reinforcement learning (RL) algorithm to achieve this goal. Specifically, we design a unique RL environment that empowers the RL algorithm to fit multiple highway curves. Our experimental results demonstrate the superiority of our method over other methods.

Relationship between Horizontal Curve Geometry and Single-Vehicle Crash Occurrence on Rural Secondary Highways

Single-vehicle crashes are overrepresented on rural two-lane highway curves. While prior work investigated the relationship between crash occurrence and aggregate curve characteristics, several important aspects related to curve geometry remain uninvestigated. To this end, research was undertaken to evaluate the safety effects associated with several specific horizontal curve-related geometric characteristics (including curve type, curve direction, tangent distance between curves, and curve design speed) on rural two-lane undivided highways, considering non-animal single-vehicle crashes. Eight years of crash data were obtained for 277 mi and 557 mi of curved state and county highway segments, respectively, within Michigan. Several mixed-effects negative binomial models, with county- and site-specific random intercepts, were developed separately for state and county highways. The model results indicated that several key geometric factors were associated with crash occurrence on rural two-lane highways, including curve type, curve direction, tangent distance approaching the curve, inner-curve tangent distance, and curve design speed. Each of the following geometric characteristics was associated with elevated single-vehicle crash occurrence: (1) compound and reverse curves (compared with simple curves); (2) left-turning curves (compared with right-turning); (3) curves with design speeds lower than the speed limit (compared with curves with higher design speeds); (4) longer tangent distances approaching a simple curve or the initial curve in a series; and (5) shorter inner-curve distances between successive compound or reverse curves. Compound or reverse curves should be avoided in favor of simple curves with an elongated inner-curve distance. Enhanced warning signage should be considered where such curve designs cannot be avoided.

An Efficient Path Planning Method for the Unmanned Aerial Vehicle in Highway Inspection Scenarios

Unmanned aerial vehicles (UAVs) have received widespread attention due to their flexible deployment characteristics. Automated airports equipped with UAVs are expected to become important equipment for improving quality and reducing costs in many inspection scenarios. This paper focuses on the automated inspection business of UAVs dispatched by automated airports in highway scenarios. On the basis of considering the shape of highway curves, inspection targets, and the energy consumption characteristics of UAVs, planning the flight parameters of UAVs is of great significance for ensuring the effectiveness of the inspection process. This paper first sets the inspection path points for the UAV based on highway curves, and then proposes an efficient heuristic method for the nonlinear non-convex parameter optimization problem, through which the parameters of the UAV’s inspection altitude, hovering altitude, and flight speed are planned. Simulation and analysis show that the proposed method possesses good parameter planning efficiency. By combining several existing trajectory planning methods, e.g., the traversal method, the deep Q-network based method, and the genetic method, it can be concluded that the proposed method in this paper has better overall planning performance including planning efficiency and inspection effectiveness.

Do Dynamic speed feedback signs impact drivers differently based on speeding tendencies? Insights from applications at select critical roadway contexts

The effects of a traffic control devices on drivers at different speed percentiles, particularly on the faster drivers, are of specific interest due to their higher likelihood of crash involvement. A study was designed to evaluate how the dynamic speed feedback signs (DSFS) affect drivers while transitioning from a high-speed to a low-speed environment. A total of 5 sites were selected, which included a freeway exit ramp, two speed transition zones, and two high-speed rural highway curves. Vehicle speed profiles approaching and entering these critical locations were collected before and after installing the DSFS. Based on the tracked speed of the free-flowing vehicles before the influence area, drivers were categorized as slower drivers, average drivers, and faster drivers using the 15th and 85th percentile speed at each site. Overall, installing the DSFS resulted in a significant reduction in speed across all locations for all sites. Drivers were found to reduce their speed while approaching the curve, traversing through the speed transition zones, and entering the curves or reduced speed limit areas. Results showed that faster drivers tend to reduce speed more than the average or slower drivers at every location. The faster drivers also reacted to the sign earlier compared to the slower or average drivers. The overall results are encouraging as they indicate that DSFS impact faster drivers more, which can ultimately reduce speeding-related crashes when transitioning from a high-speed environment. Based on the findings, the continued use of DSFS as a speed reduction strategy is recommended.

Crash Prediction Modeling for Horizontal Curves on Two-Lane, Two-Way Rural Highways Based on Consistency and Self-Explaining Characteristics Using Zero-Truncated Data

Consistency and self-explaining characteristics play important roles in road safety performance, especially at rural highway curves. This study aims to take into account the effect of several contributing factors associated with consistency and self-explaining. The scope is limited to the roads based on the crash frequency that occurred at horizontal curves of Two-Lane, Two-Way Rural Highways (TLTWRHs). The main contribution is to simultaneously consider the traffic, geometry, consistency, and self-explaining variables, as novel parameters, for a set of 224 selected horizontal curves of TLTWRHs in Iran. The curves with existing at least one fatal crash in their history for the three-year period, from 2018 to 2020, have been selected as a case study. The collected data was zero-truncated and under-dispersion. The modeling process was carried out using the Poisson, Zero-Truncated Poisson (ZTP), and Conway-Maxwell-Poisson (COM-Poisson) regression models followed by analyzing the results. The results showed that the COM-Poisson regression model could effectively be used in the case of under-dispersed zero-truncated crash data and demonstrated that there are strong relationships between the crash frequency and the consistency variables: the ratio of curve radius to the average radius of the adjacent curves (as the alignment consistency variable) and the difference between expected and existing superelevation (as the vehicle stability consistency variable). Furthermore, the findings indicated enhancing the Field of View (FOV), as one of the self-explaining characteristics of the roads, is an effective low-cost approach for improving road safety on TLTWRH horizontal curves, compared to the other measures. Moreover, the results confirmed that constructing TLTWRH self-explaining horizontal curves is four times more effective than improving its consistency in terms of crash reduction meanwhile the curve self-explaining is 33% more effective than the superelevation improvement of TLTWRH curves.

Evaluating Driver Response to a Dynamic Speed Feedback Sign at Rural Highway Curves

Research was performed to assess the effectiveness of a dynamic speed feedback sign (DSFS) as a speed reduction countermeasure when installed at horizontal curves on rural highways. It was of particular interest to assess whether the DSFS effectiveness varied based on curve advisory speed and to identify the optimal DSFS placement location with respect to the curve. A series of field evaluations were performed at five horizontal curves located along two-lane rural state highways in northern Michigan possessing posted speed limits of 65 mph and curve advisory speeds varying between 25 and 60 mph. The DSFSs were installed and evaluated at two different locations at each curve: 1. at the curve advance warning/advisory speed sign and 2. at the point of curvature. Vehicle speeds were tracked along the approach to each curve using handheld LIDAR guns. The results indicate that the DSFS was generally more effective at reducing motorists’ speeds when installed near the advance curve warning sign. Furthermore, the DSFS was more effective at locations with sharper curvature (i.e., lower advisory speeds). Continued use of DSFSs as a speed reduction countermeasure on rural horizontal curves is recommended, particularly at locations with a significant differential (e.g., at least 25 mph) between the upstream speed limit and the curve advisory speed. The DSFS should be positioned near the advance curve warning/advisory speed sign to provide adequate time for drivers to react and decelerate before reaching the curve.

Fuzzy Reliability Calculation Method of Highway Alignment

Considering the randomness and fuzziness of highway route design parameters, based on the reliability theory and triangular fuzzy numbers, the fuzzy variables are transformed into random variables. Three new fuzzy reliability calculation methods of highway alignment are derived, namely, the equivalent density function method, the information entropy method, and the general density function method. The proposed calculation methods are applied to the reliability analysis of highway horizontal curve design. The results show that if the fuzzy variables are symmetric fuzzy numbers, the equivalent mean values obtained by the three methods are equal. If the fuzzy variables are asymmetric fuzzy numbers, the equivalent mean values and equivalent standard deviations of the three methods are different. Compared with the traditional reliability calculation method, the values obtained by the proposed method have a large reliability index, small failure probability, and high calculation accuracy. Compared with the other two methods, the general density function method has the fastest convergence and higher accuracy. The general density function method is then applied to the calculation of highway circular curve radius, under the condition of a superelevation failure rate of 5%, to generate the recommended values of the safety and reliability index.

Evaluation of Pavement Runoff and Driving Safety on Highway Curve Segment

Runoff depth distribution on the concave and circular curve sections is obtained from a two-dimensional numerical simulating model in order to analyze the temporal and spatial variation of the pavement runoff on the curve section. The two-dimensional model verified by the field data can depict the alignment of pavement more accurately as compared to the empirical equation and a one-dimensional model. The runoff on the concave section and circular curve section is compared for the free water drainage and centerline drainage. Results show that a two-dimensional model is essential for the analysis of the centerline drainage. The runoff depth can be controlled by a reasonable curb height and location interval. The drainage type affects the variation of the runoff depth on the nearside lane, and the maximum water depth can be up to more than 80 mm on the concave section and nearly 60 mm on the circular curve section under centerline drainage. Besides the existing hydroplaning results, the runoff depth difference of the wheel trace should be considered to evaluate driving safety. Sideslip will occur when the depth difference becomes more than 6 mm under condition that the runoff depth is less than the tread depth (7 mm). When the runoff depth is more than the tread depth, sideslip will occur once the depth difference exceeds 4 mm.

Analysis of the properties of new forms of transitional sections of railway and highway curves

The properties of new forms of transitional sections of curves of railways and highways are largely determined by the specific features of the design and functioning of the systems “railway line-rolling stock” and “driver-car-road”. Taking them into account had a significant impact on the formalization of targets and criteria for the quality of the functioning of these systems, as well as on the mathematical means and methods of their achievement. The results obtained in this case significantly differ from the traditional ones. The geometric differences between the transitional sections of railways are in the nonlinear regularities of strictly monotonic, G4 smooth changes in the curvature of their line axis and G3 smooth cross slope, which are described by non-identical functions with variable properties. At the same time, the quality of movement, assessed at the design level of the rolling stock, is ensured by the harmonization of the length of the transition section and the variable properties of its functions with the given characteristics of other properties of the system. The differences between the transitional sections of highways consist in the inclusion of the calculated speed and the speed of its change directly into the principle of the trajectory curvature of vehicles. This ensures the safety and convenience of curvilinear movement of cars on them both at constant and variable speeds. The theoretically substantiated potential for the improvement of the quality of functioning of these systems with the proposed solutions determines the reasonability of their comprehensive testing in practice and further improvement of the theory, norms and rules for the design of transitional sections of curved rail and highways.

Solution Method and Application Verification of the K-curve as a Highway Transition Curve

Because of the singular form and low flexibility of the clothoid as a highway transition curve in highway horizontal alignment, the K-curve, whose ratio of the chord-tangent angle to the tangential angle at any point is fixed, was proposed in a previous work, including the corresponding parametric equations and basic characteristics, and its high flexibility and various shapes were proved. Here, the application and verification of the K-curve in highway alignment is further studied. The solution methods of the K-curve for different connections are given. Through theoretical calculations and specific real-world examples, the geometric positions and lateral forces of the K-curve and the clothoid under different connection conditions are compared. The results show that the difference between the K-curve and clothoid in the above two aspects under a straight line-to-circle connection is greater than that under a circle-to-circle connection as an egg curve, and although the lateral force coefficient of the K-curve is smaller than that of the clothoid, the K-curve suffers from rapid change in the lateral force coefficient and a higher lateral acceleration change rate. Finally, the application conditions of the K-curve for highway alignment design are given with consideration of the centrifugal acceleration change rate.

Effectiveness of Warning Piles on Driving Behavior on the Curve of Low-Grade Highway

To develop a scientific and practicable guideline for implementing warning piles on Chinese low-grade highways, it is necessary to study the effect of warning piles on driving performance in different road alignments and environments. Based on a driving simulator, this paper evaluates the effect of unilateral and bilateral warning piles on vehicle speed and lateral position on a two-lane rural highway curve with different road geometries. The results show a significant effect of bilateral warning piles on speed control, which becomes more obvious as the radius of the curve decreases and the superelevation increases. In sharp curves, vehicle speed increases rapidly in the second half of the curve, and bilateral warning piles could significantly control speed increase to prevent danger. Meanwhile, the effect of bilateral warning piles on keeping vehicles in a safer lane position is also statistically significant in the second half of the curve. With a decreasing radius and an increasing superelevation, the value of the maximum lateral position will increase. Bilateral warning piles could reduce the lateral position to keep the vehicle on a stable track. Moreover, bilateral warning piles could also perform better at night. This paper studies both unilateral and bilateral warning piles’ effects on driving behavior in different road geometries, thus providing a theoretical basis for the engineering application of warning piles.

Curves used in highway design and Bezier curves

Curves used in highway design and Bezier curves

Estimation of Vehicle Carbon Emissions in China Accounting for Vertical Curve Effects

Predicting vehicle carbon emissions on vertical curve sections can provide guidance for low-carbon vertical profile designs. Given that the influence of vertical curve design indicators on the fuel consumption and CO2 emissions of vehicles are underexplored, this study filled this research gap by establishing a theoretical carbon emission model of vehicles on vertical curve sections. The carbon emission model was established based on Xu’s vehicle energy conversion model, the conversion model of energy, fuel consumption, and CO2 emissions. The accuracy of the theoretical carbon emission model and the CO2 emission rules on vertical curve sections were verified by field test results. Field tests were carried out on flat sections, longitudinal slope sections, and various types of vertical curve sections, with five common types of vehicles maintaining cruising speed. The carbon emission rate effects on the vertical curve are closely related to the gradient and irrelevant of the radius. On the vertical profile composed with downhill/asymmetric/symmetrical vertical curve with a gradient greater than the balance gradient, the carbon emission rate is determined by the gradient and radius. The influence of the gradient on carbon emissions of vehicle on these vertical profiles was more significant than the radius. The radius is irrelevant to the carbon emission rate on the other forms of vertical profile. These results may benefit highway designers and engineers by providing guidelines regarding the environmental effects of highway vertical curve indexes.

Analysis of Single-Vehicle Roadway Departure Crashes on Rural Curved Segments Accounting for Unobserved Heterogeneity

Roadway departure crashes are one of the core emphasis areas in Strategic Highway Safety Plans (SHSP). These crashes, especially on rural roads, lead to a disproportionately higher number of fatalities and serious injuries. The focus of this study is to identify and quantify the factors affecting injury-severity outcomes for single-vehicle roadway departure (SV-RwD) crashes on rural curved segments in Minnesota. The crash data are extracted from the Highway Safety Information System (HSIS) from 2010 to 2014. This study applied a mixed logit with heterogeneity in means and variances approach to model driver-injury severity. The approach accounts for possible unobserved heterogeneity in the data resulting from driver, roadway, traffic, environmental conditions, or any combination of these attributes. This analysis adds value to the growing body of literature because it uncovers some unobserved heterogeneity in the form the attributes specific to driver-injury severities in contrast to the standard mixed logit approach. The model results indicate that there is a complex interaction of driver characteristics and actions (male drivers, aged below 30 years of age, and unsafe speed), roadway and traffic characteristics (two-lane undivided road, county roadways, and low traffic volume), environmental conditions (adverse weather, cloudy weather, dark conditions, and dry surface conditions), and vehicle characteristics (vehicle type—sport utility vehicle involved in rollover crashes). The results also provide some evidence of the effectiveness of a highway curve safety improvement program implemented in one of the Minnesota Department of Transportation (DOT) districts.

Cross-Sectional Study of Vehicle Speeds on Rural Four-Lane Highway Curves

Research has consistently shown that horizontal curves are often associated with increased crash rates compared with similar tangent highway sections. These crashes are often related to speed and the difficulty of judging the severity of the curve. Curve speed models are used for a variety of applications, including assessing operational characteristics, evaluating design speed, conducting spot safety analyses, and setting curve advisory speeds. However, most of the documented curve speed models apply to rural two-lane highways, while relatively few models have been developed for rural multilane highways. These types of highways may exhibit different driver behavior in curves because of their more generous geometric design and higher traffic volumes. The objective of this paper is to document models that have been developed for several types of rural four-lane highways, including undivided highways, divided highways, and freeways. The authors developed models that account for geometric characteristics like curve radius, superelevation rate, and deflection angle, as well as operational characteristics like approach tangent (TN) speed. These models were calibrated using a database of about 46,000 vehicles across 29 horizontal curve sites in central Texas.

Effect of geometry on driver heart rate

Driving is a complex task incorporating most of the body organs and sensory system. Coordinated performance of eyes, ears, hands and legs are required in harmony with mental or cerebral actuations. Depending upon the stimulus the cardio vascular performance of a driver varies. The objective of this paper is to model the heart rate kinetics of drivers in response to variation in highway curve geometry. The study was done on 114 horizontal curves of two lane rural highways of Kerala. Heart rates of 30 drivers were collected during their drive along the study stretches. Cross sectional details of curve like radius of curve, length of curve, deflection angle, superelevation, width of road, width of shoulder and available sight distance were measured. Similarly the length of preceding tangent to the curve was also considered. Findings of the study revealed the correlation of sight distance and shoulder width with average heart rate. A nonlinear regression model was proposed based on analysis.

The influence rule of highway curve radius on speed perception and operating speed

In order to understand the influence of the radius of horizontal curve on driver’s speed perception, driving simulation experiments were carried out in the route scene with radius from 400 m to 1000m based on Uc-win/road driving simulation system. The real-time speed and acceleration parameters of the whole section of the vehicle were collected by ECO driver plug-in built in the software, and the driver’s perception speed at feature points is acquired by “inquiry method”. The perceptual speed and actual speed at the feature points are compared and analyzed. The results show that when the roadside environment is monotonous, the perceptual speed of the driver is lower than the actual speed, and the perceptual speed near the entry curve is much lower than the actual speed. However, the radius of the curve has little effect on the estimation error of vehicle speed at the turning point., after the midpoint of the curve, the accuracy of drivers’ perception of speed is gradually improved; when the radius of the horizontal curve is large, the speed of the vehicle is not affected by the radius of the curve.

3D Highway Curve Reconstruction From Mobile Laser Scanning Point Clouds

The point clouds acquired by a vehicle-borne mobile laser scanning (MLS) system have shown great potential for many applications such as intelligent transportation systems, road infrastructure inventories, and high-definition (HD) maps to support the advanced driver-assistance systems (ADAS) and autonomous vehicles (AVs). This paper presents a novel two-step approach to automated detection and reconstruction of three-dimensional (3D) highway curves from MLS point clouds. However, when dealing with noisy, unstructured, dense point clouds, we often face some challenges, most notably in handling of the outliers introduced during road marking detection and in recognition of curve types during 3D curve reconstruction. Our approach is formed by two main algorithms: a detector based on intensity variance and a robust model fitting estimator. The experimental results obtained using both a virtual scan dataset and a real MLS dataset demonstrated that our approach is very promising in handling of the outliers and reconstruction of 3D road curves. Specifically, a relative accuracy of 0.6% has been achieved in estimation of circle radii based on the virtual scan dataset. A comparative study also showed that our road marking detection approach is more effective and more stable than state-of-the-art approaches.

Evaluating the effectiveness of perceptual treatments on sharp curves: a driving simulator study

Objective: Speed has been identified as a key risk factor in road crashes, influencing the occurrence of a road crash and its severity. Excessive speeding is particularly dangerous on highway curves, and under critical traffic and environmental conditions. Various measures have been identified to be effective in managing and controlling vehicle speed. Among these, low-cost perceptual measures have been considered to be effective tools, as they generally increase the risks perceived by drivers, or alter speed perception, and consequently lead the drivers to reduce their speeds. The overall aim of this study is 1) to investigate the effectiveness of a set of perceptual treatments in reducing the driver’s speed along a sharp curve of an existing rural road that is characterized by high crash rates, and 2) to identify the most effective measure(s) to implement in the field to counteract the problem of speeding.Methods: A driving simulator study was developed and four speed-reducing measures (white and red peripheral transverse bars (PTB), optical speed bars (OSB) and chevrons) were tested on a sample of forty-two drivers. The driving speeds recorded using the treatments tests were compared to a baseline condition (treatments were not applied). Subjective measures were also collected; these included the driver’s evaluation of the desired speed, risk perception, road legibility, and markings comprehension, as based on screenshot pictures that represented the simulated configurations of the treatments.Results: The outcomes demonstrated an overall effectiveness of the perceptual treatments. Particularly, red PTB were associated with a speed-reduction of up to 12 km/h along the curve under study. An analysis of the questionnaires revealed that drivers did not fully comprehend the relevant message of PTB. Despite that, the drivers did unconsciously reduce their speeds; this confirms the effectiveness of such perceptual treatments based on the optical illusion that entices drivers to reduce their speeds.Conclusions: The findings demonstrated the effectiveness of the perceptual treatments, especially red PTB, in enticing drivers to reduce their speeds whilst approaching the sharp curve under study or driving through the curve.

Association of Carbon Emissions and Circular Curve in Northwestern China

Carbon emissions, produced by automobile fuel consumption, are termed as the key reason leading to global warming. The highway circular curve constitutes a major factor impacting vehicle carbon emissions. It is deemed quite essential to investigate the association existing between circular curve and carbon emissions. On the basis of the IPCC carbon emission conversion methodology, the current research work put forward a carbon emission conversion methodology suitable for China’s diesel status. There are 99 groups’ test data of diesel trucks during the trip, which were attained on 23 circular curves in northwestern China. The test road type was key arterial roads having a design speed greater than or equal to 60 km/h, besides having no roundabouts and crossings. Carbon emission data were generated with the use of carbon emission conversion methodologies and fuel consumption data from field tests. As the results suggested, carbon emissions decline with the increase in the radius of circular curve. A carbon emission quantitative model was established with the radius and length of circular curve, coupled with the initial velocity as the key impacting factors. In comparison with carbon emissions under circular curve section and flat section scenarios, the minimum curve radius impacting carbon emissions is 500 m. This research work provided herein a tool for the quantification of carbon emissions and a reference for a low-carbon highway design.