Exploratory Advanced Research . . . Next Generation Transportation Solutions

The Exploratory Advanced Research Program Fact Sheet

One of the major traffic bottlenecks and safety concerns on today’s 

busy roads occurs during freeway 

merges. “Advanced Freeway Merge 

Assistance: Harnessing the Potential of 

Connected Vehicles” is an Exploratory 

Advanced Research (EAR) Program 

project designed to improve the 

efficiency and safety of freeway 

merges using connected vehicle 

technology. This project was awarded 

by the Federal Highway Administration 

(FHWA) in 2009, and was conducted 

by the University of Virginia Center for 

Transportation Studies (UVA CTS).

Efficient and Safe Merging Solutions 

Advanced Freeway Merge Assistance: Harnessing the Potential 

of Connected Vehicles

Utilizing Connected Vehicle 

Technology

The Connected Vehicles Program is an initiative 

designed to enable wireless communications 

among vehicles, the highway infrastructure, and 

travelers’ personal communications devices. 

UVA CTS aimed to develop and evaluate 

candidate freeway merge assistance systems 

that might significantly improve operations in a 

connected-vehicle environment. UVA CTS 

created a connected vehicle traffic simulation 

tool over a 3-year development process with 

funding from the National Science Foundation, 

FHWA, and the Virginia and California 

Departments of Transportation. 

Using a previous 2008 study on the ability of 

connected vehicle technology to improve ramp 

metering as the starting point for this study, the 

project developed and evaluated strategic 

algorithms designed to improve freeway 

merging. These algorithms were developed 

specifically to take advantage of the capabilities 

provided by the system. 

Improved Merging Algorithms

The freeway merge assistance system consisted 

of three algorithms: dynamic lane control, gapresponsive on-ramp signal, and merging 

control. Dynamic lane control encourages 

lateral movements of mainline vehicles by using 

a lower speed limit for the far right lane of the 

freeway. A gap-responsive on-ramp signal 

algorithm will give a ramp vehicle the green 

light based on the expected gap availability in 

the freeway mainline. As these algorithms were 

previously developed, the project focused on 

enhancing and refining them. Finally, the 

revolutionary merging control algorithm 

controls and advises speed changes for both 

mainline and ramp vehicles in order to allow for 

merging in the smallest space, at the highest 

speed possible.

Expanding Research

According to Bob Ferlis of FHWA, “This project 

provides a comprehensive means to address 

freeway merging. The team at UVA CTS 

successfully built upon and extended the 

results of previous ramp metering research to 

deliver improvements in efficiency and driver 

safety when merging.”

One of the major objectives of this project 

was to utilize the communication capabilities of 

connected vehicle technology. The research 

team integrated microscopic transportation 

simulations with wireless network simulations. 

The results from both simulations helped in 

designing control actions associated with 

freeway merging.

A safety evaluation module was also 

developed to assess safety impacts under 

various scenarios. This module is unique in that 

it generates a projected number of crashes. 

Vehicle trajectories reconstructed from actual 

crash data were also investigated to explore 
drivers’ response time as a contributing factor, 

as well as the potential to prevent crashes either 

by sending an alert to the driver, or else by using 

automated action where drivers would not have 

time to respond themselves. 

Future Benefits

This research has the potential to significantly 

improve freeway merge areas, which present 

significant bottleneck and safety concerns 

today. The project can also help prepare 

transportation agencies to make full use of 

connected vehicle technology as it emerges.

“Ultimately the project is expected to create 

freeway merge areas with greater capacity and 

fewer crashes,” says Ferlis. “The algorithms 

under development here will continue to take 

advantage of emerging connected vehicle 

capabilities to improve the safety and efficiency 

of future freeway merge operations.”

For vehicle, system, and equipment 

manufacturers to build on these results in the 

future, additional research will be needed to 

further develop the concept of operations, 

understand its value, and to identify promising 

deployment scenarios. Success at this stage of 

research could lead to further traffic simulation 

studies with higher-level controls for the freeway 

and its environs. Also, additional simulations 

could be conducted using a driving simulator to 

assess the receptivity of people to advice, or 

control actions taken in response to the concept 

of operations. Success could eventually lead to 

testing a prototype on a closed course to 

identify further technical questions, assess 

human factors issues, and to support technology 

transfer activities.

Learn More

For more information on this EAR Program 

project, contact Bob Ferlis at FHWA, at 

202-493-3268 (email: robert.ferlis@dot.gov).

Publication No. 

FHWA-HRT-14-045

HRTM-30/02-14(1M)E

Efficient and Safe Merging Solutions 

Advanced Freeway Merge Assistance: Harnessing the Potential of Connected Vehicles

Image other side: 

This is a merge sign by the 

road side with sky as 

background.

© www.istockphoto.com/

zxcynosure

Traffic merging onto freeway.

©www.istockphoto.com/Joe_Potato

What Is the Exploratory 

Advanced Research Program?

FHWA’s Exploratory Advanced Research 

(EAR) Program focuses on long-term, highrisk research with a high payoff potential. 

The program addresses underlying gaps 

faced by applied highway research 

programs, anticipates emerging issues 

with national implications, and reflects 

broad transportation industry goals and 

objectives. 

To learn more about the EAR Program, 

visit the Exploratory Advanced Research 

Web site at www.fhwa.dot.gov/

advancedresearch. The site features 

information on research solicitations, 

updates on ongoing research, links to 

published materials, summaries of past 

EAR Program events, and details on 

upcoming events. For additional 

information, contact David Kuehn at FHWA, 

202-493-3414 (email: david.kuehn@dot.gov), 

or Terry Halkyard at FHWA, 202-493-3467 

(email: terry.halkyard@dot.gov).