Reduce Vehicle Speeds Research Articles

인천항 대기오염물질 배출량 산정 및 저감효과 분석

As global awareness of air pollution issues caused by ports increases, international organizations and developed countries are monitoring pollution levels and establishing various eco-friendly policies to reduce emissions. Domestically, the relevant laws were enacted in 2020 to systematically manage the sources of port pollutants in the five major ports. This study aims to estimate the emissions of air pollutants generated by Incheon Port and analyze the effects of major eco-friendly policies such as Emission Control Areas (ECA), Vehicle Speed Reduction (VSR), and Alternative Maritime Power (AMP). For the year 2023, activity data for all ships, cargo handling equipment, and vehicles were collected, applying methodologies from reputable institutions such as the European Environment Agency (EEA) and the Environmental Protection Agency (EPA). According to national guidelines, air pollutants are categorized into eight types: CO, NOx, SOx, TSP, PM10, PM2.5, VOC, and NH3. The analysis revealed that the total emissions of air pollutants from Incheon Port were approximately 6,362 tons, with ships accounting for over 60% of the total emissions. Among the pollutants, NOx was the highest at 4,597.4 tons, followed by CO at 862.4 tons, and TSP at 314.6 tons. Among the ports, emissions were highest at the New Port, followed by the South Port, Inner Port, and North Port. The results of this study provide essential baseline data for monitoring the air pollution levels of Incheon Port and serve as critical evidence for environmental management and policy development. For sustainable future management, it is crucial to secure reliable data and develop a platform that links data collection, analysis, and visualization functions for more systematic operation.

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.

Bus rapid transit as arterial corridor traffic calming: The relationship between transit infrastructure and motor vehicle operating speeds

Objectives This article presents an analysis of the traffic-calming effects of bus rapid transit (BRT) by studying changes to motor vehicle speeds before and after implementation of Albuquerque Rapid Transit (ART) infrastructure in Albuquerque, New Mexico. Methods While ART construction was completed in spring 2018, the BRT buses did not operate until December 2019; providing a unique opportunity to explore the influence of BRT infrastructure sans BRT buses (i.e., to tease apart the effects of BRT infrastructure and operations). We used validated data from StreetLight InSight to compare before/after changes to average motor vehicle speeds and 85th percentile motor vehicle speeds at 46 ART sites and 36 control sites. Results Findings suggest that infrastructure associated with BRT systems can improve traffic safety by reducing vehicle speeds. Speed decreases at the ART sites were especially strong in terms of 85th percentile decreases, suggesting that the BRT infrastructure is especially effective at limiting excessive speeding. Motor vehicle 85th-percentile speeds along the ART corridor were reduced by 11.5% (compared to a 5.8% decrease at control sites). The 85th-percentile speeds at the ART sites decreased from 32.3 mph to 28.6 mph, which is an especially important range for vulnerable road-user safety outcomes. While ART intersections saw the largest decreases in absolute speeds (a reduction of 4.1 mph in 85th-percentile speeds), ART mid-block sites had larger decreases relative to the control mid-block sites (decreases in 85th-percentile speeds were 73.7% greater at ART mid-block sites than at control mid-block sites). BRT-related lane reductions were linked with particularly strong speed reductions; there were 85th-percentile speed reductions of 4.1 mph (12.6%) when general vehicle lanes were removed versus 2.2 mph (7.8%) when lanes were not removed. Conclusions Speed reductions were experienced across the ART corridor even though 87.0% of BRT locations did not have a change in posted speed limit, suggesting that physical changes to the roadway associated with BRT were impactful in terms of speed reductions and in turn could possibly promote traffic injury prevention by decreasing the number and severity of crashes.

Assessing Multifaceted Effects of Speed Humps and Bumps: Travel Time, Safety, and Environmental Considerations

This study focuses on investigating the significant impacts of speed breakers on various parameters, including travel time delays, vehicle speeds, fuel consumption, pavement maintenance costs, and vehicular exhaust emissions. Field data was collected and analyzed to assess the effects of different types of traffic calming measures on these parameters. The findings provide valuable insights into the implications of speed breakers on road safety, environmental pollution, and overall road infrastructure management. The results reveal that the implementation of speed humps, speed bumps, and triple bumps effectively slows down vehicles, as evidenced by considerable reductions in the 85th percentile speeds. The reduction percentages were 41.65% for speed humps, 73.52% for speed bumps, and 86.27% for triple bumps. This indicates the effectiveness of these traffic calming measures in improving road safety by reducing vehicle speeds. However, the presence of speed breakers also leads to increased travel time delays. On average, traversing stretches with speed humps, speed bumps, and triple bumps resulted in delays of 9.31, 16.42, and 29.51 seconds, respectively. While the individual delay times may appear relatively short, the cumulative effect of multiple speed obstacles along a road needs to be considered. Another significant impact observed is the increased fuel consumption associated with speed breakers. The study found that for every 100 km of travel, motorcycles and passenger cars consumed approximately 12.07 km and 27.37 km of additional fuel, respectively, when the density of speed breakers was 1.33/km. This translates to a fuel consumption increase of 13.73% for motorcycles and 37.74% for passenger cars. Furthermore, the presence of speed humps was found to contribute to pavement deterioration, as indicated by decreased Pavement Condition Index (PCI) values. The study also revealed that sections with speed humps incurred significantly higher maintenance costs compared to sections without speed humps. The increase in maintenance cost ranged from 100 to 264% across different road sections, with higher traffic volumes leading to greater cost escalation. Additionally, the study confirms that lower vehicle speeds, particularly between 0-15 km/hr, are associated with higher emissions of pollutants, including carbon monoxide (CO) and other pollutants. This highlights the environmental implications of speed breakers and their contribution to urban air pollution. Doi: 10.28991/CEJ-2024-010-07-07 Full Text: PDF

Integrating vehicle trajectory planning and arterial traffic management to facilitate eco-approach and departure deployment

Eco-approach and departure (EAD) enable continuous vehicle motion in urban signalized corridors. Since such a motion can extend to the EAD vehicles’ followers, it makes EAD a promising technology to benefit the traffic flow where automated vehicles and conventional vehicles coexist. Most existing EAD studies envision an ideal setting that neglects real-world operational conditions such as lane changes, multi-movement intersection configuration, partially automated fleet, and/or limited traffic state awareness. This study aims to fill the gap by designing an EAD algorithm considering real-world traffic operation constraints. The proposed algorithm uses a model predictive controller to minimize vehicle speed reduction and variation based on the real-time traffic signal control plan and measured queues at the intersection. The required inputs are readily available at many modern intersections. We observed that the proposed controller’s performance might degrade because of lane-changing maneuvers and lead-left turn traffic signals. These observations motivated our development of a lane change management strategy and a signal control implementation strategy to facilitate the EAD implementation. The lane change management strategies separate the EAD operations and lane-changing maneuvers in time and space. The signal control implementation strategy applies lag-left turn signals to enable EAD operation for both the through and left-turn vehicles. Compared to the non-EAD case, our EAD approach produces 2.5% to 7.8% energy savings while keeping similar intersection mobility. Notably, this approach brings about 2.5% to 3.6% energy savings in a 2% CAV case. This result demonstrates the feasibility of deploying EAD at low connected automated vehicle penetration rates.

Evaluation of the physical barrier on lane segregation at multilane highway towards motorcyclist: A case study

Abstract In Malaysia, the escalating annual road traffic accidents, primarily attributed to human factors, necessitate a closer examination of these influences. This study focuses on assessing the impact of lane segregation on motorcyclists’ behavior within multilane roadways. Conducted along the R5 highway from Kapar to Kuala Selangor, classified as a rural highway, the study evaluates the 85th percentile operating speed, crucial for multilane flow rate. Two locations, one with median physical barriers and the other with only line markings, were compared. Traffic flow and speed were observed at 5-minute intervals over 45 minutes using a laser gun and tally counter. Analysis, based on the Malaysian Highway Capacity Manual, revealed that the median barrier location promoted safe speeds and a higher motorcycle percentage. Conversely, the absence of a median barrier but with line markings resulted in elevated speeds exceeding the limit, accompanied by a lower motorcycle percentage. These findings underscore the significance of median physical barriers in reducing vehicle speed, enhancing road safety, and curbing road accidents.

Battery Management for Improved Performance in Hybrid Electric Vehicles

This study aims to improve the battery performance in hybrid electric vehicles (HEVs) by reducing the vehicle speed. We developed a specific protocol for managing battery use and optimizing the energy consumption rate to achieve this goal. The protocol automatically controls the driving operation, avoiding incompatible driving patterns with an energy-saving mode and performance improvement. This protocol was applied to a simulation process to predict energy rate lowering and battery performance enhancement. The proposed protocol applies to any hybrid electric vehicle type and any route conditions since it uses vehicle mass, drag and rolling coefficients, and road slope as variable parameters to determine the minimum energy consumption rate. We performed experimental tests to validate the simulation data and the proposed protocol. Furthermore, the protocol applies to variable starting vehicle speeds, from 10 to 50 km/h, corresponding to the current driving patterns, sport, normal, and eco, set up by car manufacturers. A reduction of 10% in vehicle speed in urban and peripheral routes achieves a minimum energy rate, enhancing battery management. Current vehicle speed shows a deviation from optimum management of 18% while applying vehicle speed reduction limits the deviation to 0.2%. Experimental results show a good agreement with simulation data, with 94% accuracy. We tested the protocol for urban and peripheral routes with maximum vehicle speed limits of 60 and 90 km/h.

Ecologically Oriented Freeway Control Methods Integrated Speed Limits and Ramp Toll Booths Layout

Traffic exhaust pollution, especially in congested areas of freeways, is one of the main causes of air pollution. With the increase in the number of vehicles, traffic and environmental issues have become more prominent. In addition, traffic congestion leads to frequent starting and stopping of vehicles, further exacerbating environmental pollution. This article focuses on the problem of frequent starting and stopping of vehicles, using variable speed limit control to smooth traffic flow, reduce vehicle speed, and alleviate exhaust emissions caused by traffic congestion. At the same time, considering the traffic and environmental benefits of bottleneck areas on freeways, the VT-Micro model is used to calculate exhaust emissions, and a coordinated control method for the mainline and ramp of freeways is proposed. The simulation experiment results show that the total driving time of the mainline and ramp collaborative control method considering environmental benefits has been reduced by 24.69%, CO emissions have been reduced by 4.79%, HC emissions have been reduced by 7.65%, NOx emissions have been reduced by 2.48%, and fuel consumption has been reduced by 4.98%.

Solar Lights for Highways with Zone-Wise Speed Control System for Vehicle

The challenge of providing adequate lighting along highways, particularly at critical points such as sharp turns and speed breakers, poses significant safety concerns. Traditional energy sources often fail to meet the demands of continuous lighting, especially in remote areas. To tackle this challenge, we present an automatic lighting system aimed at selectively activating lights during nighttime while also reducing vehicle speed near or at danger zones. Entire system is designed as automatic, human involvement is not required; lights are controlled automatically by sensing the vehicles. Whenever the vehicle enters into the danger zone, lights will be energized and they remain in ON state until the vehicle leaves that area. The system will be activated automatically during dark. In this method precious energy acquired from the solar panel can be saved. During the day time the battery will be charged and this stored energy is utilized in the nights[10]. It is a novel approach to vehicle navigation and safety implementation, and also aimed at automatically sensing the areas/zones like Schools, Hospital Accident, etc and automatically reducing the speed of the vehicle for safety purposes.

Road Bump Detection and Voice Alert System Using YOLOv8 and gTTS

Roadway bumps present a significant hazard to drivers, leading to discomfort, vehicle damage, and even accidents. This research paper proposes an innovative solution for bump detection and driver/vehicle response using advanced artificial intelligence (AI) techniques. This research paper explores the application of the YOLOv8 algorithm for detecting road bumps and generating voice alerts to enhance road safety. The proposed system utilizes a camera based approach installed in vehicles to detect road bumps in real-time. Upon detection, a voice alert is generated using the gTTS library, informing the driver of an impending bump ("Bump is near you"). The primary objective is to provide drivers with timely information to reduce vehicle speed and avoid discomfort or potential accidents caused by road bumps. Additionally, the paper discusses the feasibility of integrating this AI algorithm into car systems to automate speed reduction when bumps are detected. By leveraging sensors and advanced algorithms, car companies could enhance vehicle safety by ensuring that vehicles automatically slow down upon approaching a road bump, mitigating the risk of accidents and minimizing wear and tear on vehicles. Furthermore, the study investigates the impact of road bumps on accidents, emphasizing the importance of early detection and driver awareness. By addressing this issue, the proposed system aims to contribute to improved road safety, reduced accident rates, and enhanced driving experience for all road users.

Development of Empirical Equation to Estimate Corridor Speed of Vehicles in Metro Construction Work Zone

Abstract Construction of elevated metro line leads to a reduction in the average speed of vehicles due to congestions, diversions, and road incidents. This reduction in speed depends on recurring (e.g., congestion in rush hours) and non-recurring (e.g., road accidents) delay factors. Non-recurring factors involve incidents such as accidental bus stops, pedestrian crossings, or clearing debris from road, etc., some of which may occur at very short notice. This research paper presents a case study of Pune Metro Rail Construction (Corridor II) in India for developing an empirical equation to estimate corridor speed of vehicles in metro construction work zone. Observations were recorded in spatial and temporal zones using floating car method through video recordings and traffic count using manual method. Based on the traffic behavior pattern, five non-recurring delay factors (NRDFs) were defined, namely vehicles in lateral entry, slow moving vehicles, vehicles in the wrong direction, on-street parked vehicles, pedestrian interference and their correlation with speed of vehicles was tested. It was concluded that these factors have a strong negative correlation with the speed of the test vehicle. To estimate corridor speed with given NRDFs, nonlinear equation was formulated using empirical evidence and validated using larger simulated data.

Assessing the Impacts of Merge and Speed Control Strategies on Highway Work Zone Safety and Operations Using Artificial Intelligence and Advanced Sensors

Speed management and merge control are two critical factors influencing highway work zone safety and operations. This study adopts artificial intelligence (AI) and advanced radar and thermal camera sensors to generate detailed vehicle trajectory and speed data, which are used to quantify the impacts of various Traffic control strategies on driver behavior as well as on work zone safety and operations. The strategies considered include transverse rumble strips, flashing speed limit signs, dynamic message signs, and different lane closure taper lengths. Among these strategies, flashing speed limit signs are found to significantly reduce vehicle speeds when approaching the lane closure point.

Analysis Of Apal Cue Time, Queue Length, And Delay Using Pkji 2023

The intersection of Kyai Haji Wahid Hasyim and Mataram Sewer Inspection Road, Dabag, Condongcatur, Depok District, Seman Regency, Yogyakarta. Initial observations show that the intersection is often congested due to heavy traffic flow, especially during peak hours. Congestion in the city of Yogyakarta, especially the sleman district, is unavoidable, especially at intersection points both on protocol roads and on small roads. This congestion can result in losses for road users such as reduced vehicle speed, increased waiting time, increased vehicle queues, and decreased environmental quality. to reduce this congestion, researchers analyzed the time of the apill signal, queue length, and delay so that the congestion could be resolved. Determine the right alternative to solve the problems contained in the intersection. Primary data collection was carried out in the field for seven days with peak hours in the morning at 07.00-08.00 WIB and in the afternoon at 16.30-17.30 WIB using CCTV as a traffic volume data counter. Traffic light signal data is obtained in the field by counting each approach. Secondary data used is obtained from the Population-related Service Agency such as the Central Bureau of Statistics. The data obtained is then analyzed using the Indonesian Road Capacity Guidelines 2023 (PKJI 2023) Signalized Intersection method. The highest capacity analysis results on October 02, 2023 with a vehicle volume of 2539 kend / hour. With the result time of all red time north direction 1 second, south direction 1.09 seconds, east direction 0.43 seconds, west direction 0.42 seconds. and green time lost a total of 17 seconds. Queue length in the north direction 160.19m, in the south direction 186.96m, in the east direction 54.48m, in the west direction 115.3m. Delay in the north direction 71.45 seconds. In the south direction 72.4 seconds, in the east direction 59.56 seconds, in the west direction 60.66 seconds.

The adoption and application of Intelligent Speed Assistance by private motorists: User and non-user perspectives

Intelligent Speed Assistance (ISA) is an in-car system that can help drivers to avoid speeding and therefore reduce crash frequency and severity. ISA systems that intervene to reduce vehicle speeds are increasingly available in new cars. Their efficacy in crash reduction will depend on the extent to which they are adopted and used by motorists. Increasing ISA use is therefore a promising new target for behaviour-change interventions seeking to reduce crash involvement. To provide context for intervention development, this study explored the beliefs and attitudes of 20 car drivers who have intervening ISA systems and 20 that do not. Thematic analysis of interview scripts generated five superordinate themes across both sets of drivers relating to: (1) safety, (2) driver control, (3) choice and enforcement, (4) driver identity and behaviour, and (5) enabling roll-out. ISA acceptability was generally high as long as driver choice around turning off and overriding the system was maintained. Drivers described a number of information needs relating to ISA: increased general awareness of ISA, provision of system-specific information for new ISA drivers and reassurances around non-ISA driver concerns (e.g., the responsiveness of the override and the speed control process). Many drivers indicated that ISA adoption would be facilitated by emphasising personal benefits (e.g., protecting driver licences, reduced insurance premiums, improved fuel efficiency, more relaxed driving) as well as safety advantages.

Development of Policy Guidance for Temporary Rumble Strips

Temporary rumble strips are used by state departments of transportation (DOTs) to help reduce vehicle speeds in work zones and to alert drivers they are approaching a work zone. A research study was undertaken to develop policy guidance for the use of temporary rumble strips by DOTs. The research methodology included a review of existing literature, synthesis of DOT practices, and field observations of driver behavior and installation of temporary rumble strips. This paper presents the first known assessment of DOT practices for both long-term and short-term temporary rumble strips in the United States. Field observations noted minimal erratic driver behavior (1/8636) such as swerving to avoid the temporary rumble strips. A synthesis of 18 existing DOT practices found differences in levels of implementation and standards for temporary rumble strips among DOTs. Concerns noted by DOTs and installation personnel include the heavy weight of short-term temporary rumble strips, requirements for installation, worker exposure to traffic, potential for erratic driver behavior, and the need for maintenance of the temporary rumble strips. Suggested modifications to existing DOT practices were developed to address these concerns and potentially reduce cost, increase installation efficiency, enhance worker safety, and improve performance of temporary rumble strips.

VEHICLE ACCIDENT AVOIDANCE WITH ROAD ADVERSE CONDITIONS MONITORING SYSTEMS

Accidents are the leading cause of death in emerging nations. Despite the fact that "speed kills," individuals still don't care enough to drive safely on ghat roads. The most pressing issues now are ghat road accidents and the deaths that result from them. There will be sharp turns and narrow roadways on mountain highways. Under these kinds of circumstances, a driver of a vehicle cannot see vehicles and animals travelling on the highways from the other side. This issue results in the deaths of thousands of people and animals every year. The answer to this issue is to warn the driver in the GHATs section of any approaching vehicles or animals. In order to achieve this, "INFRARED SENSORS and LED LIGHTS" are kept on either side of the road before the curve. This way, if a vehicle approaches from one end of the curve, the sensor detects it and the LED light shines on the opposite side. Drivers can be vigilant and reduce vehicle speed by observing the LED light on/off criteria. Keywords- Alerting system, Infrared sensor, LED, Buzzer.

How to reduce pedestrian fatalities: a case-by-case study to evaluate the potential of vehicle and road infrastructure interventions

In line with the UN’s global goals on sustainability several initiatives are promoting walking. However, if effective interventions are not implemented an increased number of pedestrians will lead to more road casualties. It is important to take appropriate decisions on interventions to reach Vision Zero adopted by the Swedish Government. This study describes the characteristics of fatal crashes with pedestrians on Swedish roads and investigates the potential of different vehicle and road infrastructure interventions to save lives. The Swedish Transport Administration (STA) in-depth database of fatal crashes was used for a case-by-case investigation. Out of the 226 fatally injured pedestrians during 2011–2016 in Sweden the most common accident scenario was a vehicle hitting a pedestrian while crossing the road. Most crashes occurred in darkness on rural roads (63%), but for urban areas the majority (53%) occurred in daylight. In general, interventions related to vehicle speed were found to address a larger proportion of the studied pedestrian fatalities on urban roads compared to on rural roads, while separated pedestrian paths outside the carriageway were found to address a larger proportion on rural roads compared to on urban roads. The intervention with the largest total potential was pedestrian crossings with speed calming measures for the motor vehicles, which had the potential to address 36% of the identified fatalities. A reduced speed limit in combination with speed calming interventions had the potential to prevent 29% of the studied fatalities while separate pedestrian paths outside the carriageway had the potential to prevent approximately 15%. It was estimated that the vehicle safety technology with the highest potential was autonomous emergency braking with pedestrian detection for passenger cars. With this system available on all cars, 58% of the studied fatalities could potentially be prevented. Most (up to 93%) of the studied fatally injured pedestrians could potentially be saved with known vehicle safety and road infrastructural technologies. However, the analysis of the potential effect of interventions show that it will take a long time until the advanced and potentially effective vehicle safety technologies will be widely spread. This shows the importance of speeding up the implementation. A fast implementation of effective interventions in the road infrastructure is also necessary, preferably using a plan for prioritization. There are two main approaches of doing that, separating road user groups, or reducing vehicle speeds in areas with mixed rod user groups to survivable levels, which is recommended to be 30 km/h. There is a need to identify areas where most pedestrian accidents occur and then use the most effective interventions. The results of this study could be helpful in this process.

Effect of urban morphology and greening on noise and air pollution - case studies including disease burden estimates

Exposure of both noise and air pollution due to road traffic in urban environments has been calculated and evaluated for multiple cases assuming constant total traffic flow. A model study in an urban setting used 31 cases of building morphologies and traffic concentration. An evaluating second set was based on a real case of an arterial road transformed into a boulevard. Besides the effect of building morphology, the effects of driving speed, electric vehicles and urban greening were studied. The levels of noise exposure (Lden and Lnight at housing facades) and air pollution (NO2 and PM10 at sidewalks and yards) were calculated as input to estimating the health impact using DALY (Disability-Adjusted Life Years) per person. Openings in building blocks were shown to impair the noise situation but improve air quality. Nonconflicting positive results were shown for several solutions including densification by complementing the blocks with towers, transitioning to electric vehicles in combination with reduced vehicle speed, and traffic concentration by locating all local traffic to a single, widened road. Urban greening was shown to improve the noise situation whereas air quality varied due to the interaction between wind speed, dispersion, and filtering effect of leaves.

Examining the Impact of Distance Between VSL Road Signs on Vehicle Speed Variance

Variable speed limit (VSL) is an intelligent transportation system (ITS) solution for traffic management. The speed limits can be changed dynamically to adapt to traffic conditions such as visibility and traffic volume, curvature, and grip coefficient of the road surface. The VSL traffic sign location problem and attempts to solve it using computer simulation are presented in this paper. Experiments on a selected road segment, carried out using the traffic simulator, have shown that the proposed method allows the driver’s habits to be taken into account so that the location of road signs can be optimized. The observable effect was a reduction in vehicle speeds and speed variance on critical road segments, translating directly into increased safety and harmonized traffic.

Evaluating Driver Response to an Advanced Speed Display near Uncontrolled Median Openings

Uncontrolled median openings contribute to more road crashes because drivers do not obey traffic laws such as driving between lanes and following speed limits. This study examined the effectiveness of the different types of signs near an uncontrolled median opening in Mahmoud Abad, Iran. There were Signs 1 and 2 with a single message, while Signs 3 and 4 contained multi-messages. An Internet of Things (IoT) test system was developed to collect and record vehicle speed data before and after each sign installation. Results showed that speeding behavior decreased almost immediately after the road signs were installed and remained almost constant until the beginning of uncontrolled median openings. Moreover, multi-message traffic signs reduce vehicle speeds twice as much as single-message signs. Additionally, only multi-message signs are effective at reducing speed limit violations.