Search

This study aims to reduce air pollution caused by vehicle emissions in confined spaces and realize low-carbon travel in urban underwater tunnels. Based on the MEET (Methodologies for Estimating Air Pollutant Emissions from Transport) and COPERT (Computer Programme to Calculate Emissions from Road Transport) models, combined with real vehicle test data, an urban underwater tunnel speed–CO2 emissions factor model was constructed. Results show that: Different working conditions have a great impact on the MEET model; load and slope factors expand the actual CO2 emissions factor, which is different from the actual situation. The CO2 emissions factor in the COPERT model is negatively correlated with the speed, and there are fewer variables in the model, so the parameters are more controllable and more in line with the actual situation. According to the vehicle gasoline consumption and taking CO2, i > GC as the judgment index, the optimal limit speed of the ramp is calculated to be 40 km/h, while the main line maintains the existing state of 60 km/h. The model is simple and easy to operate, can be applied to estimate vehicle CO2 emissions factor at underwater tunnels in other cities, providing a basis for traffic management and effectively realizing low-carbon travel. [ABSTRACT FROM AUTHOR]

Coalbed methane (CBM) resources cannot be efficiently explored and exploited without a robust understanding of the permeability of fracture-size heterogeneities in coal. In this study, two sister coal samples were imparted with pre-developed cleat and connected fractures, and the permeability of the coal samples was measured under different conditions of controlled confining and gas pressures. Furthermore, the implications of the results for CBM exploration and exploitation were discussed. The permeability of coal with cleat development ranged from 0.001–0.01 mD, indicating ultra-low permeability coal. The gas migration in this coal changed from a linear flow to a non-linear flow, with the increase in gas pressure (>1 MPa). Thus, the permeability of the coal initially increased and then decreased. However, the Klinkenberg effect does not exist in this ultralow-permeability coal. For the coal sample with connected fracture, permeability ranged from 0.1–10 mD, which is larger by hundred orders of magnitude than that of the sample with cleat. For this coal, with a decrease in gas pressure (<1 MPa), the Klinkenberg effect significantly increased the permeability of the coal. With an increase in the applied confining pressure, both the Klinkenberg coefficient and permeability of the coal presented a decreasing trend. It is suggested that field fracture investigation is a prerequisite and indispensable step for successful CBM production. The coal beds that cleat network is well conductive to the connected fracture can be an improved target area for CBM production. During CBM production, a variety of flow regimes are available owing to the decrease in CBM reservoir pressure. In particular, under the low CBM reservoir pressure and low in situ geo-stress conditions, the gas migration in the CBM reservoir with connected facture development exhibits remarkable free-molecular flow. Thus, the reservoir permeability and predicted CBM production will be enhanced. [ABSTRACT FROM AUTHOR]

To investigate the impact of traffic pricing policies on energy consumption, this study shows a microeconomic quantitative analysis scheme to simulate individual consumption behaviors from a microeconomic viewpoint. Energy consumption is estimated based on individual demand of non-mobility goods and mobility goods under nine policy scenarios based on strategies of gasoline tax adding and mass transit fare reduction independently or combined. Results show that gasoline tax adding has strong effects on consumption behaviors. Energy consumption reduces mostly because of less consumption of non-mobility goods and car trips. However, policy of mass transit fare reduction has limited impact on energy saving because consumption of non-mobility goods and mass transit trips increases, but the number of car trips decline by only a small percentage. Comparing with single-type policy, policies that combined gasoline tax adding and mass transit fare reduction show less energy consumption. Findings suggest that policies that increase cost of car trips, such as gasoline tax adding, are very helpful to reduce the consumption of non-mobility goods and car trips, which contribute to less energy consumption. However, reducing cost of mass transit trips suggests limited effect on energy saving. Copyright © 2015 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

• Confined driving environment of the tunnel will aggravate driver's nervousness. • Longitudinal right-of-way is mainly reflected in the tunnel alignment perception. • Driver's attention mainly focuses on the far front area. • For some facilities, alignment and contour guidance varies in inverse proportion. • Alignment and contour guidance facilities are conducive to spatial right-of-way. Urban road tunnel construction is becoming ever more prevalent, and traffic safety in tunnel operation is even more important. This study evaluates the influence of different visual guiding facilities on drivers' spatial right-of-way perception by combining quantitative and qualitative methods in order to provide a basis for traffic safety optimization in the tunnel. Simulation scenes were designed for six common types of visual guiding facilities as comprising no facility (baseline), horizontal strips, edge markers, LED arch, vertical stripes, and combination (multiple) facilities. An eye tracker was used to obtain eye movement data of subject drivers exposed to various scenes. After each driving test, psychological feeling of the subjects in tunnel driving, and their ratings of alignment and contour guidance of various facilities were obtained by questionnaires. The research results showed that setting locations and facility types have a great impact on drivers' glance location and glance duration. When horizontal stripes, edge markers, LED arch and vertical stripes were set separately, alignment guidance and contour guidance performance were found to vary in inverse proportion. Horizontal stripes and edge markers are the preferred and necessary facilities, which are conducive to ensuring longitudinal and horizontal rights-of-way. LED arch and vertical stripes are also good supplements to spatial right-of-way. The combination of these 4 types of facilities can provide multi-level alignment guidance and contour guidance functions, which is beneficial to traffic safety in the tunnel. [ABSTRACT FROM AUTHOR]

• Self-explaining performance of vertically facilities for SSES and PRT is better. • The closer actual speed of the test scene is to the SSES, the greater PRT. • Combined of contour and alignment guidance can play better self-explaining effect. A low-cost and effective speed control method is to be developed for urban road tunnels in order to enhance traffic safety and improve operation in the tunnels. The self-explaining performance of the visual guiding facilities on driver's speed perception and reaction time in the interior zone of urban tunnels was investigated. Using 3D Max to build video simulation model, and referring to the common visual guiding facilities in urban tunnels, six scenes were constructed, namely no facility, horizontal stripe, edge marker, retroreflective arch, vertical stripe and multiple facilities. Stimulus of subjectively equal speed (SSES) and perception reaction time (PRT) were selected as the basic performance indicators to evaluate the different scenes. The experimental results showed that the SSES in multiple facilities scene was closest to the standard speed, followed by the vertical stripe, retroreflective arch, horizontal stripe, and no facility, while speed over-estimation was the most serious in edge marker scene. The results of PRT also showed that self-explaining performance of PRT in multiple facilities and vertical stripe scenes was better than other facilities. Vertically spaced facilities had better SSES and PRT self-explaining performance. The reasonable combination of different types of visual guiding facilities can integrate the advantages of each facility, which is more conducive to realizing the self-explaining effect of rapid perception, accurate judgment, timely decision and easy manipulation. [ABSTRACT FROM AUTHOR]

• Presence of the psychological and physiological inconsistency phenomenon at tunnel exit. • Slack effect induces an abnormal acceleration of the tunnel exit. • Coupling of slack effect and white hole effect. • Slack effect threatens traffic safety. In this paper, the causes of frequent traffic accidents at the exits of highway tunnels are investigated. This study recruited 34 subjects to conduct vehicle experiments using an illumination meter, eye tracker, Smarter Eye and OBD to measure the illumination, eye movement characteristics, driving trajectory, and speed while driving in a tunnel exit. A questionnaire was used to investigate drivers' subjective feelings while driving. The change trend of each indicator in the area near the tunnel exit was analyzed, and the relationships among the light environment, driver physiology, driving behavior, and driver psychology were explored. The psychological and physiological inconsistency phenomenon and abnormal acceleration behavior were observed at the tunnel exit, and the slack effect was verified. As the tunnel exit area is driven through, with the rapid increase in illumination, the rate of change of the driver's pupil area increases, and the distance between the vehicle and the tunnel sidewall increases. It is unreasonable that in a tunnel exit with a poor traffic environment, some drivers experience psychological slack and tend to increase their speed and accelerate out of the tunnel. The slack effect is observed in most drivers, approximately 79.4% of the total. The white hole effect interferes with drivers' vision and reduces their ability to obtain traffic information. The slack effect reduces drivers' attention and increases vehicle speed. A coupling effect exists between the white hole and slack effects, which together threaten traffic safety at the tunnel exit. [ABSTRACT FROM AUTHOR]

• Point-shaped facility only enhance lateral right-of-way. • Retroreflective ring is the only facility that improve longitudinal right-of-way. • The combination of these facilities can meet the requirements of spatial right-of-way. In order to investigate whether retroreflective rings can enhance drivers' perception of spatial right-of-way in freeway tunnels, this paper explores a simulation test. The characteristics of spatial right-of-way in tunnels are elucidated, and a comparative test is conducted using commonly used delineators and raised pavement markers against retroreflective rings to enhance the perception of spatial right-of-way. The test employs the perception of lateral deviation and longitudinal distance as indicators to reflect the lateral and longitudinal right-of-way. Video scenarios, incorporating different facilities and spacing, are created using 3Ds Max software following the design standards of freeway tunnels. The indicators of Stimulation of Subjectively Equal Distance (SSED), lateral deviation, and perception reaction time (PRT) are chosen to assess the effects of different facilities on drivers under varying spacing conditions. Fifty-two participants, divided into two groups of novice drivers and experienced drivers, underwent perception testing in a simulated driving environment. The results indicate that drivers exhibit the highest overestimation of longitudinal distance and the longest PRT of lateral deviation in the absence of facilities. Installing retroreflective rings with a spacing of 50–200 m significantly mitigates the overestimation of longitudinal distance, while reducing the PRT of lateral deviation. On the other hand, setting up delineators and raised pavement markers with a spacing of 6–12 m significantly reduces the PRT of lateral deviation, while there is no significant enhancement to the perception of longitudinal distance. A spacing of 200 m for retroreflective rings and 10 m for delineators and raised pavement markers in the straight section is recommended as a safer and more economical setting scheme. The combination of these facilities can enhance drivers' safety perception of spatial right-of-way in freeway tunnels, facilitating rapid perception, correct judgment, and timely decision-making for the safe passage of vehicles. [ABSTRACT FROM AUTHOR]

• Examining drivers' visual load in highway tunnel connection zones. • Revealing how upstream tunnel length affects driver comfort and strain. • Establishing a critical zone length to safeguard drivers from visual strain. • Shedding light on adaptation times and pupil area changes in varied tunnel scenarios. • Investigating driver comfort during transition zones within tunnel groups. To investigate drivers' visual load and comfort in the distance between adjacent tunnels (tunnel group connection zones), the maximum transient vibration value (MTVV) of the pupil area is used in this study as the index to analyze the visual load characteristics of the driver throughout the connection zones in highway tunnel groups. Data was collected using field driving experiments during which the pupil area change rate is measured as an additional indicator to evaluate the sufficiency of the length of the connection zones from the perspective of drivers' visual adaptation. The findings show that the length of the upstream tunnel affects the visual strain of the drivers when they enter the connection zone. The visual load and its association with the length of the upstream tunnel appeared to be in the following descending order: short > extra-long > long > medium tunnel. The visual discomfort level in the short upstream tunnel has shown to be "uncomfortable," while the level of comfort slightly rises to "fairly uncomfortable," in the connection zone when the upstream tunnel is extra long and long. Departing from medium upstream tunnel resulted in the highest level of comfort "a little uncomfortable level" in the connection zone. When the upstream tunnels are short and medium in length, the required time for light adaptation is 5 s. The connection zone length threshold which is the minimum length of connection zone in order for two consecutive tunnels not to affect each other in terms of visual load of drivers is calculated to be 713.89 m. The driver's pupil area change during light adaptation when the upstream tunnel is short and medium is in the range of 30–40 %. When upstream tunnel is long and extremely long, the light adaptation time is 8 s and 9 s, respectively, and the respective thresholds for connection zone are 797.22 m and 825 m. The drivers' pupil area change in long and extremely long tunnels during light adaptation is in the range of 38–50 % and 43–50 %, respectively. Findings in this study can be used for the design of connection zones between tunnels in a highway tunnel group. [ABSTRACT FROM AUTHOR]