Materials engineers at NASA have just created an exciting new tire that could help to improve transport over rough, extraterrestrial terrain. Jumping off of the original concept that helped the moon buggy zip around on the surface of the Moon, metal wheels with steel springs, the team is applying new advances in materials science. The result is a new type of metal spring tire made of a nickel-titanium alloy instead of steel. Futurism (November 27, 2017)
by Tracy Zafian, Research Fellow
The headline of a Canadian news article last year, warned that “We may never see self-driving cars anywhere it snows.” That article discussed the experiences of Sam Abuelsamid, a former automotive engineer turned tech writer and his experience with cars’ automated assist features in snowy conditions. One snowy day, as Abuelsamid drove around, his car’s radar sensor became covered with slush. As a result the car’s adaptive cruise control (ACC) disengaged, and an alert was given that the radar sensor needed to be cleaned off before the ACC could be used again. Abuelsamid surmised that to use the ACC in these weather conditions, he would need to pull over and clean off the radar sensor repeatedly as he kept driving. He chose to keep the adaptive cruise control disengaged instead. In another example, Abuelsamid was in a parking lot and there were large fluffy snowflakes falling. The car’s parking assist sensors detected the snowflakes and thought they were potential obstacles, thereby triggering repeated audible alerts to warn of their presence.
Can autonomous vehicles be taught to be smarter than this, and will they ever be able to perform well in the snow? Some car manufacturers including Ford and General Motors have been testing self-driving cars in snowy conditions and the results are promising.
One issue in the winter, as mentioned above, is that the sensors and cameras for vehicle safety features can be covered with snow or ice. This can happen even with new non-autonomous vehicles and as described in this winter’s safety guide, it’s important to keep them clean. Some car manufacturers are using small wipers or defrost technology to keep the sensors and cameras clear.
Ford, similar to other companies, has been developing high fidelity 3D maps of the roads its self-driving cars will travel. The maps include road geometries and line markings, road signs, and other nearby features. Ford’s self-driving cars have numerous sensors and cameras, including a LIDAR (LIght Detection And Ranging) sensor on the top of the car which provides a 360-degree view, radar, and cameras on the front, back and sides of the vehicle. With these detailed maps, even if some data aren’t available at a particular time, a Ford self-driving car could still have enough information to know its location, the location of other road users, and potential hazards. This demo video shows a self-driving car in snowy conditions at Ford’s full-scale outdoor test facility in Michigan.
Researchers at the Massachusetts Institute of Technology (MIT) Lincoln Laboratory have been creating maps of roadway sub-surfaces, for use by self-driving cars. This mapping involves the use of Localizing Ground-Penetrating Radar (LGPR). To generate the maps, the LGPR equipment is mounted on the undersize of a vehicle to collect data during an initial drive. On future drives, the LGPR data is compared to the base map generated early to determine an autonomous vehicle’s location. One advantage of the LGPR approach to localization in that it doesn’t rely at all on optical images of the roadway or surrounding environment which could be obscured in certain weather conditions. This video describes MIT’s LGPR technique in more detail.
In testing with autonomous vehicles in snowy conditions, both Ford’s and MIT’s approaches have been shown to allow autonomous cars to achieve locational accuracy within a few centimeters. One possible limitation of these methods, at least at the writing of this article, , is that they both depend on detailed mapping of the roadway environment and for MIT, the subterranean environment- in clear weather conditions, in advance. This means that autonomous vehicles using such mapping can only “drive” on roadways which have already been mapped to the detailed level needed.
By Courtney Murtagh, UMTC Research staff
This past fall, both the Institute of Transportation Engineers (ITE) and the Federal Highway Administration, made important updates to their transportation research tools.
The ITE released the 10th edition Trip Generation Manual, which consists of two volumes: volume one- Desk reference and volume two- Land use data plots. It also comes with the third edition trip generation handbook, and a new web-based application titled ITETripGen.
The updated manual provides a detailed description of both vehicle and person-based trip generation data for all different settings including urban, suburban, and rural areas. The data set of land use description and plots for all land use/time period/independent variable combinations has been updated with twenty-two new land use classification for more than 1,700 sites. The new desktop app allows users to access the entire trip generation data-set electronically, with plenty of filtering options including site setting, geographic location, age of data, development size, and trip type.
The Federal Highway Administration updated their Interactive Highway Safety Design Model (IHSDM),is a software analysis tool used to evaluate highway designs expected safety and performance based on data collected from existing highways.
The tool now includes an economic analysis option (EA Tool). The purpose of the new EA tool is to allow project managers, highway designers, and others using the tool to estimate the cost of crashes predicted for one or more designs and run benefit-cost analyses. Data has also been updated on the app, which now includes a lane offset option for urban and suburban arterials. Minor graphical user interface, output/reporting, documentation, and system administration tools were updated to adapt to the new EA Tool.
Both these changes are significant to improve safety in highway designs, and improved modeling and design for transportation engineers.
by Tracy Zafian, UMTC Research Fellow
On the evening of September 30, 2017, a road construction worker in Ohio, Steve Cook, age 59, was hit and killed by an impaired driver while in a work zone. Just before the crash, the driver looked down at his cell phone. Not only distracted, the driver had also been drinking. He now faces charges of vehicular manslaughter.
Roadway work zones can be hazardous both for drivers and for workers on site. The latest data from the Federal Highway Administration show that in 2015 nationwide, there were an estimated 96,626 crashes in work zones an increase of 8% over 2014. Of these crashes, 642 (0.7%) involved at least one fatality.
On average, 85% of work zone fatalities are drivers or passengers in cars. Of the fatal crashes in 2014, major contributing factors included speeding (28%), lack of seatbelt use (25%), alcohol (25%), and distraction (16%). Approximately 40% of fatal crashes in work zones are rear-end collisions. When compared to 16% of all fatal crashes nationwide, this is a huge percentage. It also provides insight into areas for improvement.
States have approached this issue a few different ways. Some have focused on safety campaigns, others on enforcement and some states have looked into technology to help decrease these crashes. Most safety campaigns encourage drivers to drive more slower and be alert in work zones. Almost all states have increased fines for speeding or other traffic violations in work zones. In Massachusetts and many other states, the fines in work zones are doubled.
Illinois, which has had a general prohibition against handheld cell phone use while driving since 2014, has banned hands-free cell phone use in work zones. Arkansas banned handheld cell phone use while driving in work zones in 2011. Wisconsin is another state specifically banning handheld cellphone use by drivers in construction zones. Wisconsin’s ban took effect in October 2016, and after one year, it isn’t clear it’s having the desired effect. Since the ban started, and combined with increased enforcement, new work zone signage, and a safety campaign, the number of work zone crashes is up and many people are still using their cell phones in work zones. According to David Pabst, Director of Safety for the Wisconsin Department of Transportation, “It’s still a problem, and we haven’t gotten the message through to people to put their phone down in a work zone.”
Massachusetts has been looking at engineering and technology options for improved work zone safety. In June 2016, the Massachusetts Department of Transportation (MassDOT) established a Work Zone Safety Task Force with members from a number of MassDOT divisions, the Massachusetts State Police, the Executive Office of Public Safety and Security, the Massachusetts Sherriffs’ Association and Construction Industries of Massachusetts. The Work Zone Safety Task Force issued recommendations in early 2017 and MassDOT is now in the process of implementing a number of new safety enhancements in work zones, including portable rumble strips at the beginning of work zones, and flashing blue LED lights on portable trailers in work zones, to simulate the presence of a police vehicle. Pilot testing of trailers with these blue lights has been conducted at construction zones along Route 2 and Interstate 190.
There are a number of additional technology options that could be considered moving forward., including using communication technologies. IBM-designed SmartCones use wireless technology to alert construction zone workers to potential threats. SmartCones placed strategically ahead of a work zone have been shown to be effective at alerting drivers about the work area and at slowing traffic.
Researchers at the University of Transportation Center in Alabama recently evaluated a number of different intrusion sensing and alarm technologies for alerting construction zone workers when a vehicle has errantly entered their active work area. Led by Eric Marks, Ph.D., the research team compared different options including kinematic, infrared, pneumatic, microwave, radar, and radio technologies, and then field tested two commercially-available systems: Intellicone Safelane and the Traffic Guard Worker Alert System. Both systems are portable and easy to deploy around a work site. Both use sensors that detect intrusion and then wirelessly send signals to an alarm system with multiple types of alerts.
In their analysis, the researchers evaluated the systems’ alarm volume, worker response time, driver response time, and vehicle stopping time and distance at different traveling speeds. The Intellicone and Traffic Guard systems performed comparably, and on average it took a worker less than 1 second to respond to the warning alerts. Based on their review and analysis, the research team recommended the Traffic Guard system for short tapers in work zones and for short-term or mobile highway construction zone projects. The Intellicone was recommended for longer tapers where traffic barrels or other longer-term temporary devices are being used. The researchers recommended the AWARE (Advanced Warning and Risk Evasion) system for safety against intrusion in longer-term work zone projects. AWARE requires the most infrastructure and setup, but provides the most comprehensive alarms.
Resource for further information: National Workzone Safety Information Clearinghouse, www.workzonesafety.org.
By Courtney Murtagh, Matt Mann and Melissa Paciulli, UMTC Research Staff
This past November, MassDOT rolled out a new tool for project management to the 365 communities in the Commonwealth. The tool titled, Massachusetts Project Intake Tool, or MaPIT, is a web-based application that helps to streamline the process for municipalities to complete the Project Need Forms (PNF) and Project Intuition Forms (PIF).
The intention behind MaPIT is to expedite the project development process, including: project initiation, environmental permitting, scoring, and project delivery. It does this by automating Project Need Form screening for relevant GIS layers, transferring PNF information to PIF forms. The application also maps project locations for public viewing. Upon approval, each project is assigned a number and its information is automatically transferred to the MassDOT Project Info Software System.
Baystate Roads, part of the UMass Transportation Center, has been offering workshops for those who wish to familiarize themselves with this new tool. The workshops include instructor-led step-by-step software training and demonstrations. The workshop trainings are aimed to help project managers, town selectmen, consulting companies, and others who would need to use the tool feel confident with the new technology. Since September seven MaPIT workshops have been held with close to 200 participants from 62 municipalities represented.
Baystate Roads has also created instructional videos to teach a wider audience about MaPIT. The videos are available online (at https://vimeo.com/umtc) and accessible to anyone who is interested at no charge.
By Tracy Zafian, UMTC Research Fellow
The use of electric buses and other zero emission vehicles (ZEVs) holds great promise to help reduce vehicle emissions and promote a clearer, less polluting transportation sector.
Transit bus systems offer a great venue for deploying and testing the latest ZEV technologies. An estimated 40 U.S. transit systems now include electric-power buses as part of their fleet. To date, bus systems in California have been the greatest adopters of electric buses. The Santa Barbara Metropolitan Transit District began using electric buses in 2003 and currently has 14 in operation. Stanford University Transit presently has a fleet of 23 electric buses, which it launched in 2014. Foothill Transit in Northern California started using electric buses in 2010 and now has 30 in use. Foothill Transit has pledged to change all its buses over to electric power by 2030. Foothill Transit estimates that already, its annual electric buses eliminate the same amount of emissions as 2,424 gasoline-powered cars. A number of other California transit agencies have smaller fleets of electric buses.
Two UMTC Research Affiliates recently developed a comprehensive review of past and current electric bus deployments nationally. This research was led by Professor Eleni Christofa in Civil and Environmental Engineering and Professor Krystal Pollitt in Environmental Health Sciences. The review included discussions of the three main types of electric-power buses currently in use, and of different facets and impacts of transit agencies’ change to electric buses, including areas of challenge.
The primary type of electric bus in use today is the battery electric (BE) bus, and more than 20 U.S. transit agencies have incorporated BE buses into their operations, including the Worcester Regional Transit Authority (WRTA) and the Pioneer Valley Transit Authority (PVTA). BE buses contain an onboard electric battery, which provides all their power. These batteries are typically re-charged through plug-in stations; BE buses also capture and then use energy from regenerative braking. BE buses have no direct vehicle emissions, but there may be atmospheric pollutants associated with the generation of electricity used for charging their onboard batteries. One potential challenge with BE buses is the short driving range (30 to 130 miles) before needing to be recharged, and the impact of the need for recharging on route scheduling. These buses will typically be recharged at bus stop charging stations during their routes for quick charges (5 to 15 minutes). Some transit agencies also utilize slower charging stations at a central location such as a bus garage, for when BE buses are out of service. Even with the quick charges, it is important that bus schedules be adjusted to reflect the charging time.
BE buses are more expensive to purchase than traditional diesel-engine buses ($750,000 per bus compared to $435,000 per bus, respectively); however, they have a longer expected lifespan than diesel buses. BE buses also save fuel and maintenance costs. Proterra has stated that overall, the lifecycle costs of BE and diesel buses are similar. The PVTA estimates that each of its BE buses will save the agency $448,000 combined in fuel and maintenance costs. The PVTA also calculated that each of its BE buses will eliminate 244,000 pounds of carbon dioxide emissions compared to their diesel bus counterparts.
The second main type of zero-emissions buses are those powered by hydrogen fuel cell batteries. Fuel cell battery electric (FCBE) buses store hydrogen onboard in storage tanks and the hydrogen is then supplied to the fuel cells to generate electricity to power the vehicles. There are no emissions, as water is the only by-product for FCBEs. There are presently seven U.S. transit agencies operating FCBE buses; the electric bus at the Massachusetts Bay Transportation Authority (MBTA) uses FCBE technology.
With a typical purchase price of $1.2 million, an FCBE bus is much more expensive to purchase than a conventional diesel bus ($435,000) or a compressed natural gas bus ($500,000). FCBE buses also require special training for bus operators on using the technology and special hydrogen storing and fueling facilities; these are typically located at bus depots to allow vehicles to be refueled at day’s end. On the plus side, the fuel economy for FCBE buses has been reported to be double that for compressed natural gas or diesel buses.
The third main type of zero emission buses are fuel cell hybrid (FCH) plug-in buses which use a combination of both onboard batteries and hydrogen fuel cells. To date, only 7 U.S. transit agencies have used FCH buses, mainly in short-term demonstration projects. Transit agencies that have tried FCH buses have consistently reported significant downtime for the buses, due to issues with the batteries, the fuel cell systems, and the hybrid integrator, and to challenges in diagnosing specific problems.
Currently, BE buses seem to hold the most promise for wider deployment and use.
by Tracy Zafian, UMTC Research Fellow
More U.S. states are considering legislation and regulations for highly automated vehicles (HAVs) testing. Twenty-four states and the District of Columbia have now enacted legislation regarding the testing of highly autonomous vehicles. Only Michigan currently allows the driverless HAVs on public roads; California is considering the same but has not approved it yet.
The federal policy (Federal Automated Vehicles Policy) provides guidance for those developing, testing, and deploying highly automated vehicles. The policy considers current and potential regulatory tools that could be used with these vehicles. The policy also describes the different responsibilities on the federal and state levels, and creates a model for state policy that recommends policy areas for states to consider for automated vehicles.
Figure 1: States with Enacted Legislation for Autonomous Vehicles
As of July 27, 2017. Source: National Conference of State Legislatures. http://www.ncsl.org/research/transportation/autonomous-vehicles-self-driving-vehicles-enacted-legislation.aspx
In October 2016, Massachusetts Gov. Charlie Baker signed Executive Order No. 572, To Promote the Testing and Deployment of Highly Automated Driving Technologies (EO 572). EO 572 created a state government working group on autonomous vehicles (AV Working Group). The group’s charge is to “convene and consult with experts on motor vehicle safety and vehicle automation…and [to] work with the Legislature on any proposed legislation necessary to protect the public welfare.” The AV Working Group is led by Katherine Fichter, Massachusetts Department of Transportation (MassDOT) Assistant Secretary for Policy Coordination and Transportation Secretary Stephanie Pollack’s designee to the group. The AV Working Group also includes other MassDOT staff and representatives from the State Police, the Executive Office of Public Safety and Security, Housing and Economic Development, and the State Legislature.
One Center, at the UMass Transportation Center, has recently contracted with UMTC Research Affiliates, at UMass Lowell, to conduct research on the technological developments, regulatory requirements, funding opportunities, and potential benefits of the emerging AV technology to take appropriate actions for the benefit of the citizens of the Commonwealth. The affiliates associated with this research are Chronis Stamatiadis, Nathan Gartner, Yuanchang Xie, and Danjue Chen. This project will provide baseline information pertaining to strategic planning for connected vehicle (CV) technologies. This information will be used by MassDOT to develop a strategic plan for the development and deployment of connected vehicle technology and infrastructure in Massachusetts.
EO 572 authorized MassDOT, with input from the AV Working Group and other technical experts, to develop and issue guidance for testing highly automated vehicles on public roadways in Massachusetts, and includes a process for companies to obtain approval for such testing.
Highly automated vehicle testing on public roadways is under the authority of MassDOT. Presently in Massachusetts, most testing takes place in spaces and courses outside of MassDOT’s jurisdiction, such as universities, private indoor testing facilities, and the former Fort Devens military base.
As described by Boston National Public Radio station WBUR, nuTonomy, a Massachusetts Institute of Technology (MIT) spinoff company, began the first testing of highly automated cars on Boston roads in January 2017. The initial testing area was limited to a 191-acre industrial park in South Boston, the Raymond L. Flynn Marine Park, which has a simple road layout, no traffic signals, and only 3 miles of roadway. At first, testing was approved only for daylight hours and good weather, but then was expanded to nighttime and inclement weather. The company has now logged over 200 miles of automated vehicle driving in the industrial park, with no crashes or incidences. With these results, in April 2017, nuTonomy was granted approval to expand its HAV testing to the Seaport and Fort Point areas. A Boston Globe article discussed this approval and interviewed City of Boston and nuTonomy staff. The Seaport roadways are considerably more complex than the testing roads so far, including more complicated intersections, traffic signals, roadways with multiple lanes, bridges, and a rotary. As before, nuTonomy’s testing in the expanded area initially was for daylight hours and good weather only.
In June 2017, MassDOT granted permission for a second MIT-spinoff company, Optimus Ride, to test highly automated vehicles on Boston roads. As described in a Boston Globe article, Optimus Ride will initially test its vehicles only in the Raymond L. Flynn Marine Park, as nuTonomy did.
During their HAV roadway testing, nuTonomy and Optimus Ride both have a human operator sitting in the driver’s seat, ready to take over control of the vehicle if needed. This is currently standard for most on-road testing of HAVs. Some companies use two human workers, one in the driver seat and one in the front passenger seat, to help sustain vigilance and monitoring of the HAV’s driving and the ability to switch to manual driving mode if ever needed. As described in its road test application to MassDOT, after 200 miles of testing, Optimus Ride may request MassDOT permission to test its vehicles with passengers.
In terms of legislation and regulations for automated vehicles (AVs), in her keynote talk at a recent conference on Autonomous and Connected Vehicles held at Worcester Polytechnic Institute, Ms. Fichter indicated that Gov. Baker and MassDOT have taken the position that it is better not to regulate AVs through legislation. AV and HAV technologies are still evolving, and legislation can be difficult to modify once passed. In the Massachusetts Legislature, there are currently eight bills that have been filed related to AVs. On July 13, 2017, the AV Working Group held a legislative meeting to discuss them and hear more about them from their proponents. The MassRobotics Consortium has posted its notes from the meeting. Most of the bills include guidance for AV safety and for liability in the event of a crash involving an AV, with no liability assigned to the original manufacturer of a vehicle that has been later converted to an AV. Joint bills S. 1945/H. 1829 also request that all AVs be zero emission vehicles (ZEVs), encourage AVs to be for public transit only in areas with dense populations, provide guidance for AV data collection, and propose having a vehicle-miles-traveled (VMT) tax on AVs. The idea of a VMT-based tax raised questions and issues at the meeting, related to such issues as geographic equity, fuel consumption and encouraging efficient vehicles, and collection of vehicle owners’ travel data, as well as the need for additional revenues as more vehicles are converted to AVs and electric vehicles.
Among the other proposed AV legislation, H. 2742 requires that AVs used for the interstate transport of goods or for transporting eight or more people be required to have a human operator present who can intervene if needed. Bills S. 1938 and H. 3422 both focus on making AVs that do not require a human operator available to the public. Bills H. 1822 and H. 1897 each request that MassDOT submit a report to the state House and Senate leaders “recommending additional legislative or regulatory action that may be required for the safe testing and operation of motor vehicles equipped with autonomous technology.” H. 1897 requests such a report by June 2017, while H. 1822 requests it by March 2019.
At the end of the July AV Working Group meeting, Ms. Fichter recommended the next meeting would be in September 2017. At this meeting, people from the AV industry will present and provide their perspectives regarding AVs and HAV regulation, and how AV technologies will come to market.
By Tracy Zafian, UMTC Research Fellow
In May 2017, Worcester Polytechnic Institute (WPI) held its second annual Connected and Autonomous Vehicles Summer School speaker series, sponsored by the Institute of Electrical and Electronics Engineers Vehicular Technology Society (IEEE VTS). The event included two days of lectures and discussions.
- Danjue Chen, Professor at UMass-Lowell and UMTC Affiliate, discussed the impacts of connected and automated vehicles (CAVs) on traffic operations and highway traffic flow, and how CAVs can help optimize roadway capacity and traffic control. Professor Chen is the featured researcher in this month’s Innovative Outlook (IO).
- Hossein Pishro-Nik, Professor at UMass-Amherst and UMTC Affiliate, spoke about Vehicular Ad Hoc Networks (VANETs) for vehicle-to-vehicle and vehicle-roadway infrastructure communications. His talk discussed the relationship between communications and safety in VANETs, how VANETs can be customized for different traffic conditions and individual drivers, and the issues of privacy in VANETs and Internet-connected devices and applications. Professor Pishro-Nik’s research is described in more detail in another post.
- Jason Rife, Professor at Tufts University, presented information on different GPS-based technologies and applications that can assist with automated vehicles and navigation, even in dense urban areas with limited sky visibility.
- Bob Sletten, Engineering Manager at Autoliv, a company that develops automotive safety systems for auto manufacturers, spoke about radar technology in automotive applications.
- Akshay Rajhans, Senior Research Scientist at MathWorks, spoke about model-based design for connected autonomous vehicles. As described in the WPI conference program, “model-based design makes use of computational models of systems under design that are developed, optimized and checked after correctness specifications throughout the design cycle.”
- Alexander Wyglinski, WPI Professor and organizer of the conference, provided an overview of vehicular communication systems and the fundamental concepts for understanding, designing, and implementing them.
The keynote speaker at the gathering was Katherine Fichter, Assistant Secretary for Policy Coordination at MassDOT. Ms. Fichter discussed the potential future impacts of driverless vehicles under different scenarios, including a Driverless Utopia and a Driverless Nightmare that were described in Driving Towards Driverless Cars, a blog by Lauren Isaac. Under these scenarios, autonomous vehicles are expected to improve roadway safety, increase vehicle miles traveled, and reduce greenhouse gas emissions, but there are other potential impacts that are less certain. For example, will more driverless cars reduce urban sprawl or increase it, and how will the mobility of low-income people be impacted? As Ms. Fichter discussed, there are questions as well about how autonomous vehicles will be regulated and insured. One big challenge is that current regulations are all based on the idea that vehicles have human operators; this will need to change.
by Hossein Pishro-Nik, University of Massachusetts-Amherst
In the future, intelligent transportation systems (ITSs) will involve connected vehicles, including driver-assisted vehicles and self-driving cars, as well as on-board mobile devices, sensors, and the software and algorithms that govern the functioning of these devices and their communications. Despite recent improvements, each year tens of thousands of lives are lost and billions of dollars are wasted because of traffic inefficiencies in the United States alone. Improvements in the transportation systems could have an enormous impact on lowering these statistics.
In this research, we aim to establish a new approach in design of safety systems, which is based on the individualization and customization of these systems to specific drivers and their environments. This means that wireless communication protocols, as well as algorithms that communicate to users, can be designed in an intelligent way in order to take advantage of all the statistical data that is available regarding the driver and his/her environment.
To accomplish this objective, we can use the technology to collect driver performance data and subsequently learn driver characteristics and driving strategies. This information, along with data collected from other vehicles and roadside units, can be used to customize the technology to each driver. With this, it is possible to adapt warnings or automatic control strategies to each driver. Meanwhile, vehicle-to-vehicle (V2V) communication can be dynamically tuned to make efficient use of finite bandwidth and guarantee the transmission of information critical to safety.
In this way, we should consider that there is an uncertainty of the message delivery between two specific vehicles, while other vehicles might also transmit simultaneously. Our research shows that by proper adaptation of wireless communication and warning algorithms, we can potentially reduce accident fatalities by a considerable amount.
To understand the benefit of V2V communication, consider a traffic stream where a chain of vehicles moves with same speed. When the first vehicle in the chain brakes, the driver of the following vehicle applies the brake after her perception reaction time (PRT). If no intervehicle communications are employed, vehicle Vi applies the brake after the sum of PRTs up to the driver i. With the communications, this time will change to the communications delay plus PRTs of the driver i. This is shown in Figure 1.
Some drivers may think that some of the received warning messages are not needed, because the drivers are aware of their own response time empirically and they know that they can react to stimuli fast. These warning messages are false alarms for these drivers. These warning messages may frustrate the drivers with an overly high number of false alarms, causing them to ignore warnings or even disable the system. To address this issue, we propose estimating the PRT of drivers and personalizing warning messages based on individual PRTs. Figure 2 shows that at the same accident probability for each driver, the false alarm rate can be reduced by at least 30% by employing the estimated individual distribution instead of the population distribution. Thus, it is of vital importance to minimize false alarms so that the system sends warnings only when they are needed.
Now, we should determine how channel access probabilities of vehicles and vehicular communications can be adapted to drivers’ characteristics. In a network of vehicles, each vehicle transmits with a specific probability in the transmission medium. Large channel access probabilities lead the system to excessive interferences and, consequently, low probability of packets being successfully received (success probability), while very small values reduce the success probabilities since the probability of the favorite transmission is low itself. Therefore, there is an optimal value, given both the physical data obtained by vehicular networks and the communications protocol requirements, which results in lower collision probability of vehicles. We can find the expression of packet success probability in a network of vehicles based on channel access probability of vehicle.
We then use a recursive algorithm to tune the transmission probability of each vehicle based on the individual characteristics of drivers. The PRT of the driver, traffic conditions, and communications delay are three factors that play roles in assigning channel access probabilities to vehicles. In simple terms, we categorize the drivers into safe and unsafe drivers based on perception-reaction time. The unsafe vehicles are the ones whose drivers have long perception-reaction time and low distance to the vehicle in front. In other words, unsafe vehicles have higher collision probability. Then we assign different channel access probabilities to unsafe and safe vehicles respectively.
Figure 3(a) illustrates the collision probabilities when channel access probabilities are assumed to be equal for all vehicles. Figure 3(b) shows the scenario in which different channel access probabilities are assigned to unsafe and safe vehicles. The minimum collision probability in the second scenario improves by 25%.
Our simulation results confirm that unsafe vehicles need to inform other vehicles of their perilous situation more frequently than do safer vehicles. In other words, with higher channel access probability for unsafe vehicles, we can achieve lower collision probabilities.
Hossein Pishro-Nik is a UMTC Research Affiliate and an Associate Professor in the Department of Electrical and Computer Engineering (ECE) at UMass-Amherst. This research was supported by the National Science Foundation under Grant CCF– 0844725 (PI: Hossein Pishro-Nik). It is a joint work with ECE PhD students Mohammad Nekoui, Ali Rakhshan, and Mohammad Kohsravi, and Professor Daiheng Ni from the UMass-Amherst Department of Civil and Environmental Engineering. For more information and access to published papers, please visit http://www.ecs.umass.edu/ece/pishro/publications.html.
By Tracy Zafian, UMTC Research Fellow
General Motors Company (GM) announced in mid-June that it completed production of 130 self-driving Chevrolet Bolt electric vehicles for testing automated vehicle (AV) technologies on-road. These highly automated vehicles (HAVs) join GM’s more than 50 Chevrolet Bolts with AV technologies already operating on public roads in San Francisco, Detroit, and Scottsdale, Arizona. In April 2017, Spectrum, the flagship magazine for the Institute of Electrical and Electronics Engineers (IEEE), reported on GM plans to have as many as 300 more self-driving vehicles on-road, presumably including the recently completed 130 vehicles. According to Spectrum, GM would then have the largest HAV fleet on-road not only in the United States, but worldwide. Google-based Waymo has the second-largest AV fleet in the United States, with an estimated 160 vehicles on-road.
In GM’s announcement regarding the 130 new self-driving Bolts, GM Chairman and CEO Mary Barra is quoted: “This production milestone brings us one step closer to making our vision of personal mobility a reality …. Expansion of our real-world test fleet will help ensure that our self-driving vehicles meet the same strict standards for safety and quality that we build into all of our vehicles.” CEO Barra has also said that “no other company today has the unique and necessary combination of technology, engineering and manufacturing ability to build autonomous vehicles at scale.”
The new self-driving version of the Chevrolet Bolt is the second generation of GM’s AVs and is capable of handling almost any roadway situation without human driver intervention. The new Bolts are equipped with the latest technologies in cameras, radar (LiDAR), sensors, and related hardware. “There are even a couple of cameras that are dedicated just to seeing traffic lights to make sure you don’t run red lights,” said Kyle Vogt, CEO of Cruise Automation, a self-driving software company that GM acquired in 2016. The GM HAVs always have an employee in the driver’s seat for safety reasons, just in case any intervention is needed. Almost all states with HAV regulations also have the requirement that a human operator be present.
In 2016, GM also partnered with and invested $500 million in ride-sharing company Lyft. In a recent Forbes article, Cruise CEO Vogt wouldn’t confirm a Reuters report that “thousands” of self-driving Chevrolet Bolt hatchbacks will go into service for ride-hailing company Lyft in 2018, but said it wouldn’t be surprising. “We’ve had a plan in place for a while and it’s going according to schedule. From what I can tell it’s much faster and going to happen much sooner than most people in the industry think,” Vogt said. “We’re planning to deploy in a rideshare environment, and very quickly.