Passenger Car Speed Research Articles

ADAPTATION OF RAIL PASSENGER CAR SUSPENSION PARAMETERS TO INDEPENDENTLY ROTATING WHEELS

This study aimed to adjust the rail passenger car running gear parameters by adapting them to independently rotating wheels. The most important aspect was the safety of the passenger car running in terms of derailment; thus, the values of the Nadal criterion were calculated first. Another aspect to consider is passenger comfort based on the values of Sperling’s comfort index according to the rail passenger car speed. The modes of suspension behaviour during operation were considered in two typical conditions: on a straight track section and on a curve with a 200-m radius. Calculations were performed using Universal Mechanism software. The results are interpreted in the paper, and the final conclusions of this study are given.

Detecting the Differences between Speed Control Bumps and Humps In terms of Speed Reduction Performances

The study was evaluated speed control undulations (SCUs), as one of the crucial speed management tools in urban areas, performance in reducing passenger car speeds. The evaluations investigated two narrow-type SCU (Bump) and two wide-type SCU (Hump) with 5 cm and 10 cm height. The performance of SCUs in reducing vehicle speeds has been examined by reading speed values from video records. Vehicle speeds have been determined at a distance from the SCUs that does not affect the speed of the drivers (approx. 125-150 m) and also at a distance of -60 m, -40 m, -20 m, 0 m (passing over), +20 m, +40 m and +60 m according to the SCU. All speed measurements were made in two different traffic flow regimes, free flow (FF) and oversaturated flow (OSF). Between the measured vehicle speeds and speed reduction rates, statistical evaluations were made for each SCU at different measurement points and the exact measurement points between different SCUs. It has been determined that the 10 cm high hump would be the right choice for reducing vehicle speeds.

Evaluation of Posted Speed Limits Reductions on Urban Roads with a High Percentage of Cyclists

This paper presents a before and after analysis of the impact of posted speed limit (PSL) changes on passenger car (FHWA class 2 vehicle) speeds in Portland, Oregon. The study focuses on urban roads, comparing sites that underwent a PSL 5-mph reduction (treatment sites) and sites where the PSL did not change (control sites). Sites with a high percentage of and priority for cyclists (neighborhood greenways) and sites with a more standard traffic composition were compared. Differences in speed characteristics such as mean and 85th percentile speeds, the speed variance, and the proportion of vehicles exceeding a speed threshold (relative to the PSL) were evaluated on aggregate and individual scales. A series of statistical hypothesis tests were employed to assess changes in the speed characteristics among individual data set pairs. The results suggest distinct differences between the treatment and control groups and neighborhood greenway and non-greenway sites. Although there is a high degree of variability, the treatment group experienced more decreases in the speed characteristics, and by a greater amount than the control group, on average. Within the treatment group, sites with a priority for cyclists were even more likely to experience a larger reduction in operating speeds. These results could be interpreted as link-level data providing indirect yet supporting evidence for the safety in numbers hypothesis and changes in motorists’ behavior on neighborhood greenways.

Using Connected Truck Trajectory Data to Compare Speeds in States with and without Differential Truck Speeds

Historically, researchers and practitioners have utilized spot speeds and microscopic simulation methodologies to evaluate the operational impact of differential or uniform speed limits for trucks and passenger vehicles. This paper presents a methodology that uses connected truck data to develop a statistical characterization of both passenger car and truck speeds. These techniques were applied to three adjacent states, Illinois, Indiana and Ohio. Illinois and Ohio have 70 mph speed limits for both trucks and cars. Indiana has a differential speed limit for heavy trucks (65 mph) and passenger cars (70 mph). The statistical distribution of truck speeds was then compared among Illinois, Indiana and Ohio. These speeds were derived from over 8 million connected truck records traveling along Interstate 70 in Illinois, Indiana and Ohio during a one-week period from May 8-14, 2022. Statistical test results over selected 20-mile sections in each state showed that median truck speeds in Indiana with its differential speed limit of 65 mph were only 1 - 2 mph lesser than the neighboring states of Illinois and Ohio who observe a uniform speed limit of 70 mph for all traffic.

Influences of Exit Advance Guide Signs on the Trajectory and Speed of Passenger Cars in Highway Tunnels

The driving behavior in highway tunnels is more complicated than that in regular roadbed sections because the former is usually affected by black and white hole effects, tunnel clearance, and bad illumination. Unfortunately, the current Chinese criteria and the Uniform Traffic Control Equipment Manual (MUTCD) 2009 guidelines provide no clear method for setting exit advance guide signs in highway tunnels. Hence, a driving simulator-based experiment was conducted in the current study to analyze the effects of exit advance guide signs on the trajectory, speed, and acceleration of passenger cars in a highway tunnel under three different service levels. It was found that when the service level is first service level, second service level, and third service level, the setting of the exit advance guide signs made the initial transverse location of the vehicle from the tunnel exit advance by 13.39%, 21.20%, and 5.73%, the lane change distance is shortened by 6.34%, 20.18%, and 15.34%, the average speed is decreased by 1.44%, 2.40%, and 0.08%, and the acceleration is decreased to −0.10 m·s−2, −0.11 m·s−2, and −0.06 m·s−2. Thus, the exit guide signs in the tunnel played a certain optimization role in improving the traffic flow state of the section and reducing the traffic accident rate.

Empirical Study of the Impacts of Bicycles on Passenger Car Speeds on Urban Roads without Bicycle Lanes

Higher bicycle mode share has been suggested as part of a solution to reduce the burden of congestion in urban areas. As strategies to promote cycling are implemented, concerns have been raised by some road users and stakeholders citing simulation-based traffic studies that indicate that an increase in the bicycle mode share generates major travel time delays via reduced vehicle speeds unless bicycle lanes are provided. The current research investigates the effects bicycles may have on motorized vehicle speeds on a variety of lower speed and volume urban roads without bicycle lanes. A detailed comparative analysis of passenger car speeds was performed using two vehicle scenarios: (i) a passenger car that was preceded by a bicycle; and (ii) a passenger car that was preceded by another passenger car. The mean and 85th percentile speeds of scenarios (i) and (ii) were analyzed using t-tests. Relationships between speed and gap times with oncoming (opposite direction) traffic were also investigated. The results indicate that, at most sites (92%), bicycles do not reduce passenger car mean speeds by more than 1 mph. Speed reductions are not generally observed in local streets or facilities with adequate gaps in oncoming traffic for overtaking.

General principles of expanding the speed range of operation of autonomous power supply systems for passenger cars

Authors address the issues of expanding the speed range for operation of autonomous power supply systems for air-conditioned passenger cars. For the first time in the domestic car construction, the issue of reducing the minimum start-up speed of a generator-drive unit arose when the passenger fleet of the Sakhalin Railway was renewed, where the speed of passenger cars is much lower than the overall network speed. Research carried out by CJSC SO TIV and JSC TVZ has shown that the use of V-belts in the modernization of the textropic-reduction-cardan drive allows solving this problem. Kinematic diagram of the drive was adopted without changes, but with the replacement of the V-belts C (B)-2360T with new narrow belts XPC-2360 without working surface wrap and with a formed tooth on the lower base. In the tensioner, the main spring with a stiffness of 75 N/mm was replaced with a spring of increased stiffness (100 N/mm). The main change was the replacement of the 2GV003 generator with a 2GV008 low-speed generator, which has a minimum rotation at full power (700 rpm). This modernization of the drive made it possible to turn on the generator 2GV008 at rated power, starting at a speed of 30 km/h. The article sets the task of expanding the speed range of operation of the EV-7 and EV-10 autonomous power supply systems for cars without air conditioning. It is solved by forcing the excitation of the generators. Analysis of modern systems of autonomous power supply of passenger cars showed that the expansion of the speed range of its operation can be achieved in three ways: • raising the gear ratio of the gearbox to ensure it is switched on to the nominal mode at a carriage speed of 15 - 20 km/h without changing the parameters of the generator and the entire system of autonomous power supply; • modernization of the electrical equipment complex for passenger cars to ensure the operation of the main power consumers and charge the battery while driving at low speeds (over 18 km/h) without changing the mechanical parameters and composition of the serial generator-drive unit; • modernization of the generator in order to reduce its turnon revolutions to the power required to provide the main power consumers without changing the mechanical parameters of the drive. All three methods have its advantages and disadvantages, the choice of any of them is determined by the technical requirements for a specific car model.

Impacts of freeway speed limit on operation speed of adjacent arterial roads

Speed limit is one of the essential factors associated with roadway safety. Spillover effect is the tendency of drivers to drive at a higher speed on relatively lower-speed non-freeway roadways after exiting higher-speed freeways. Speed studies were conducted on urban arterial roads with speed limits of 45 mph - all adjacent to freeways with speed limits of 55 mph and 70 mph. A comparison of speed differences between motorists who exited the freeway and those who were already driving on the arterial road was performed. Results showed that the mean speed and 85th percentile of passenger cars on arterials adjacent to 55 mph freeway were 47.3 and 51.1 mph, respectively, while the mean speed and 85th percentile of passenger cars on arterial adjacent to a higher speed 70 mph freeway were 49.5 and 53.4 mph, respectively. Differences in the mean speeds between vehicles exiting from freeways and vehicles already driving on the arterial road were observed at all four sites evaluated. This paper provides researchers, policymakers, and engineers with a better understanding of the effects of speed spillover on adjacent roads when determining whether to increase the speed limit on freeways.

Interpretations of Downs–Thomson paradox with median bus lane operations

The Seoul Metropolitan Government has implemented a public transportation priority policy with the introduction of a 121.1 km long of the Median Bus Lane (MBL). Therefore, to analyze the impacts of the introduction of Jongro-gu MBL in January 2018, an effect analysis using the speed and volume of passenger cars and buses in Seoul is conducted in this study. The interpretation of the Downs-Thomson (D-T) paradox demonstrates that the reduction in passenger car mode capacity can increase total social benefits. This study shows that the speeds of passenger cars and buses have reached the deterministic user equilibrium after the MBL introduction, resulting in an increase in total social benefits. Moreover, it demonstrates that the bus priority policies, which gives the right to keep the capacity of buses guaranteed in urban areas, will be effective. The interpretation of the D-T paradox will contribute to the formulation of transport demand management policies.

Evidence from Urban Roads without Bicycle Lanes on the Impact of Bicycle Traffic on Passenger Car Travel Speeds

A concern raised by some motorists in relation to the presence of bicycles on urban roads without bicycle lanes, discussed in part of the traffic literature, is that cyclists will slow down motorized vehicles and therefore create congestion. This research answers this question: do bicycles reduce passenger car travel speeds on urban roads without bicycle lanes? To answer this question, a detailed comparative analysis of the travel speeds of passenger car (class two vehicles) on lower volume urban roads without bicycle lanes is presented. Speed distributions, the mean, and the 50th and 85th percentile speeds for two scenarios were examined: (i) a passenger car that was preceded by a bicycle and (ii) a passenger car that was preceded by another passenger car. Peak hour traffic and 24-h traffic speeds were analyzed using t-tests and confidence intervals. Although a few statistically significant differences between scenarios (i) and (ii) were found, the actual speed differences were generally in the order of 1 mph or less. Therefore, differences in class two (motorized passenger) vehicle speeds with and without cyclists were found to be negligible from a practical perspective.

Application of the speed prediction model (V85) (V85) in the design of freeway interchanges

The design of freeway interchanges is performed on the basis of technical and economic comparison of options for a large number of indicators. Design decisions depend on a large number of factors: the class of intersecting streets and roads, the level of service, traffic intensity, the estimated speed at the ramps, terrain, urban development, hydrogeological conditions of construction, etc. An integral indicator of the quality of design decisions is the maximum safe speed. In most countries of the world, the speed of single passenger cars is 85 % of the security (V85), which may differ from the calculated speed at the maximum safe speed. In the article, on the basis of experimental data, empirical models for calculating speeds (V85) are obtained at freeway interchanges with directional ramps. Experimental studies were performed at freeway interchanges in the city of Moscow using a car laboratory according to the method of following the leader, as well as by processing video from a quadrocopter. The results of the study make it possible to predict the speed of movement (V85) at the ramps of freeway interchange and to compare the freeway interchanges schemes according to the criterion of speed, loss of time, relative safety and traffic capacity.

Influence of Large Vehicles on the Speed of Expressway Traffic Flow

Large vehicles impact the quality of traffic flow. To predict the impact of large‐scale vehicles on the average speed of traffic flow, vehicle speeds under different vehicle mixing rates were collected through field observations. A laser roadside traffic survey instrument with automatic vehicle type identification functionality was used to collect cross section traffic flow data. The v/C ratio, large vehicle mixing rate, and average speed of traffic were calculated for each data set. A total of 158 traffic flow data sets were captured and divided into three groups according to the v/C ratio of the expressway. The v/C ratio ranges of the three groups are v/C ≤ 0.35, 0.35 < v/C ≤ 0.55, and 0.55 < v/C ≤ 0.90. SPSS software was used to analyze the correlation between the vehicle mixing rate and the average speed under different traffic flow conditions, and a model was determined between the average speed of the vehicle flow and the large vehicle mixing rate. Analysis of the results with SPSS revealed a negative logarithmic linear relationship between the average traffic speed and the mixing rate of large vehicles. The results could also be applied to passenger cars. The models are considered as corrections of the average speed of the traffic flow after the mixing of large vehicles. When the mixing rate of large vehicles is close to zero, the forecast value of the model is the average speed of passenger cars. Furthermore, as the traffic volume of the road section increased, the influence of the mixing rate on traffic flow speed became more obvious. The adaptability of the proposed prediction model of the expressway mixing rate was verified by evaluating model predictions against actual measurements.

Evaluation of the effects of daytime running lights for passenger cars

Research trying to determine the impact of the use of daytime running lights (DRL), in vehicles, on road safety are lasting throughout the decades. The largest number of previous studies were focused on the search for a relationship between the use of daytime running lights and the number of traffic accidents. As the occurrence of accidents is affected by many factors, this paper examines whether there are differences in driveŕs estimation of passenger car speed when daytime running lights are turned on or off. In order to examine these issues in more details, driving simulator research was conducted. The respondents estimated passenger car speed of 30 km/h, 50 km/h, 70 km/h and 90 km/h, in both conditions (with and without DRL). The results of this research clearly indicate that there are differences in the estimation of passenger car speed when DRL are turned on or off. These differences are statistically significant for higher vehicle speeds (70 km/h and 90 km/h). Furthermore, demographic factors, frequency of driving, as well as involvement in traffic accidents, show significant impact on vehicle speed estimation. The recommended measures (that imply the usage of the DRL only outside of the residential areas), would greatly contribute to the protection and preservation of the environment, primarily in built-up areas.

Assessing Speed of Passenger Cars at Urban Channelized Right-Turn Roadways of Signalized Intersections

This paper aims to assess passenger cars’ speed on urban channelized right-turn roadways at signalized intersections under the free-flow traffic conditions. Stepwise regression and artificial neural network (ANN) were used to develop speed models. Geometrics data for twenty-one channelized right-turns at seventeen signalized intersections in urban areas were collected. Analysis results showed a linear relationship between right-turn roadway radius and speed. Other geometric parameters were found statistically significant at the 95% confidence level. The coefficient of determinations ( $${R}^{2})$$ was found to be 87.9%, 94.2% and 97% for the average speed, 85th percentile speed regression models and ANN model, respectively. Results obtained from the comparison analysis showed that equations developed for horizontal curves are recommended with caution for predicting speed on right-turns due to differences in the range of radius values. The regression equation $$(\hbox {Eq.}~8: V_\mathrm{avg} =10.904+0.314\,R+2.286\, \mathrm{Ds}+0.046\,\mathrm{SD}+0.288\,W)$$ developed in this study offers relatively better prediction accuracy compared to all other previous models. Besides, the ANN model outperformed all other models including the developed regression equation of this study. Care should be taken when using the findings of this study as they are exclusive to the conditions and locality under which this study was performed. To generalize the results, further validation is needed using data from different localities and drivers with diverse behaviors. In addition, models of this research are for speed predictions if curves’ radii are within the range of data used (10–135 m) in order to avoid extrapolation.

2287 - Speed Limit Policy in Michigan: The Effects on Air Pollution and Human Health

In 2017, Michigan raised the speed limit from 70 to 75 mph for passenger vehicles on 614 miles of freeways and raised the truck speed limit from 60 to 65 mph on all freeways statewide. While most of the focus of this policy change has focused on weighing the cost of safety and fuel consumption with the benefit of reduced travel times, little attention has been paid to the impact this policy will have on air pollution and human health. Speed data were collected using LIDAR speed detectors from a vehicle not readily visible to motorists. At each site, it was attempted to collect 100 readings for passenger vehicles and 10 readings for trucks in each direction, alongside volume counts. Before data consisted of 85 sites (59 study sites and 26 control sites); after data were collected for 42 sites (19 control sites and 23 increase sites). Average speed data were weighted by volume, which was used to estimate fuel economy of vehicles. Exposure data was then used to estimate the increase in fuel consumption and literature values were used to estimate the impacts to human health and air pollution. A t-test demonstrated that there was a significant increase (p<0.0001) in passenger car speeds on study segments, while speeds on control segments did not change (p=0.997). Speeds for trucks, however, significantly increased for both control and study segments (p<0.0001), which is to be expected, as the speed limit for trucks increased statewide. Passenger car speeds increased from an average of 72.0 to 74.0 mph while truck speeds increased from 61.1 to 62.7 mph along study corridors and from 61.0 to 62.5 mph along control corridors. Passenger car fuel economy did not change along control corridors and declined from 24.2 to 23.4 mpgUS along study corridors. Truck fuel economy declined from 6.4 to 6.2 mpgUS statewide. Ultimately, it was estimated that CO emissions will increase by 1,490 tonsUS, NOx by 213 tonsUS, PM2.5 by 3.32 tonsUS, and CO2 by 77,100 tonsUS annually. The greatest concern for human health is PM2.5, with costs to human health of $88,000-$130,000/metric ton. Operating speeds increased for passenger cars along study corridors, and truck operating speeds increased statewide after freeway speed limits increased. This resulted in fuel economy declining, and consequently, emissions increasing. The increase in PM2.5 emissions is the most concerning emissions increase due to the large cost to human health.

Speed Prediction Models for Trucks on Horizontal Curves of Two-Lane Rural Roads

Road safety is closely related to geometric design consistency, which is usually assessed by examining operating speed. Most consistency models only consider passenger car speeds, even though the interaction between passenger cars and heavy vehicles plays a pivotal role in road safety. This is due to the fact that there are too few models to estimate heavy vehicle speeds. This study aims to develop speed prediction models for heavy vehicles on horizontal curves of two-lane rural roads. To do this, continuous speed profiles were collected by using Global Positioning System (GPS) tracking devices on 11 road sections. Truck speeds were analyzed on 105 horizontal curves. The results showed that the radius of the horizontal curve and the grade at the point of curvature have a significant influence on heavy vehicle speeds. In this regard, vertical alignment only has a significant effect on truck speeds along upgrades. In addition, different trends were identified for loaded and unloaded trucks, so different speed models were calibrated for each of them. As a result, heavy vehicle speeds were adversely affected by grades greater than 3%. This phenomenon was larger for loaded trucks than for unloaded ones. Finally, the calibrated 85th and 15th percentile speed models were compared with those developed previously. As a conclusion, the use of the proposed models in this study was recommended on Spanish two-lane rural roads due mainly to the different characteristics of heavy vehicles around the world.

Driver responses to graphic-aided portable changeable message signs in highway work zones

ABSTRACTPortable changeable message signs (PCMSs) have been employed in highway work zones as temporary traffic control devices. Various studies showed that adding graphics to PCMS messages can provide advantages to traditional text messages, such as increasing legibility and improving the understanding of elderly drivers. This article synthesizes the findings of a two-phase research project aimed to investigate driver responses to graphic-aided PCMSs. Different text and graphic-aided PCMSs representing roadwork and flagger were set up in the upstream of highway work zones, and speed data of more than 2,700 vehicles were collected with a series of five speed sensors to determine vehicle speed reduction. Nearly 1,000 onsite driver surveys were performed to identify driver preference on the added graphics. The results discovered that graphic-aided PCMSs reduced mean vehicle speed between 13% and 17% and reduced the speed of passenger cars and trucks significantly differently depending on their locations in work zone. The results indicated that all drivers correctly interpreted the flagger graphic and two work-zone graphics, and suggested that 52% to 71% of drivers preferred to see graphics in PCMS messages. The findings also revealed that driver age did not have a significant impact on driver preference on PCMS message format.

Construction of Driving Conditions of Harbin Urban Passenger Cars

This study mainly discusses the construction of the driving cycle within passenger cars in representative districts in Harbin, China. It conducts a comparative analysis of the New European Driving Cycle (NEDC) and Japan 10-15. This study selects passenger cars in Harbin as study objects and uses GPS to analyze the data of their driving cycle and divide the collected data curves into several short segments. Then, 11 of the most representative parameters are identified to reduce and classify data by conducting principal component analysis and cluster analysis. The relative coefficient is used to extract representative driving segments. The analysis shows that the average speed of passenger cars in Harbin is approximately 15 km/h, which is lower than the conditions set in NEDC and Japan 10-15, with acceleration and deceleration speed parameters at 33.57% and 29.70%, respectively, but higher than the relative parameters in NEDC and Japan 10-15. Comparative results of characteristic parameters show that existing road parameter conditions in Europe and Japan evidently differ from those in Harbin. Driving conditions based on running data can accurately reflect local operating characteristics. This study can serve as an important reference for the design optimization, matching calculation, and control strategy optimization of new energy automobile power systems.

A Novel Approach for Operating Speed Continuous Predication Based on Alignment Space Comprehensive Index

Operating speed is a critical indicator for road alignment consistency design and safety evaluation. Although extensive studies have been conducted on operating speed prediction, few models can finish practical continuous prediction at each point along alignment on multilane highways. This study proposes a novel method to estimate the operating speed for multilane highways in China from the aspect of the three-dimensional alignment combination. Operating speed data collected in field experiments on 304 different alignment combination sections are detected by means of Global Positioning System. First, the alignment comprehensive index (ACI) is designed and introduced to describe the function accounting for alignment continuity and driving safety. The variables used in ACI include horizontal curve radius, change rate of curvature, deflection angle of curve, grade, and lane width. Second, the influence range of front and rear alignment on speed is determined on the basis of drivers’ fixation range and dynamical properties of vehicles. Furthermore, a prediction model based on exponential relationships between road alignment and speeds is designed to predict the speed of passenger cars and trucks. Finally, three common criteria are utilized to evaluate the effectiveness of the prediction models. The results indicate that the prediction models outperform the other two operating speed models for their higher prediction accuracy.

Effects of weather conditions, light conditions, and road lighting on vehicle speed.

Light conditions are known to affect the number of vehicle accidents and fatalities but the relationship between light conditions and vehicle speed is not fully understood. This study examined whether vehicle speed on roads is higher in daylight and under road lighting than in darkness, and determined the combined effects of light conditions, posted speed limit and weather conditions on driving speed. The vehicle speed of passenger cars in different light conditions (daylight, twilight, darkness, artificial light) and different weather conditions (clear weather, rain, snow) was determined using traffic and weather data collected on an hourly basis for approximately 2 years (1 September 2012–31 May 2014) at 25 locations in Sweden (17 with road lighting and eight without). In total, the data included almost 60 million vehicle passes. The data were cleaned by removing June, July, and August, which have different traffic patterns than the rest of the year. Only data from the periods 10:00 A.M.–04:00 P.M. and 06:00 P.M.–10:00 P.M. were used, to remove traffic during rush hour and at night. Multivariate adaptive regression splines was used to evaluate the overall influence of independent variables on vehicle speed and nonparametric statistical testing was applied to test for speed differences between dark–daylight, dark–twilight, and twilight–daylight, on roads with and without road lighting. The results show that vehicle speed in general depends on several independent variables. Analyses of vehicle speed and speed differences between daylight, twilight and darkness, with and without road lighting, did not reveal any differences attributable to light conditions. However, vehicle speed decreased due to rain or snow and the decrease was higher on roads without road lighting than on roads with lighting. These results suggest that the strong association between traffic accidents and darkness or low light conditions could be explained by drivers failing to adjust their speed to the reduced visibility in dark conditions.