OLR Research Report

September 22, 2008




By: Janet L. Kaminski Leduc, Senior Legislative Attorney

You asked what other states do to prevent drivers from entering a highway via an exit ramp and driving the wrong way into traffic.


About 350 people die, and thousands of others are injured, each year in the United States as a result of automobile accidents caused by wrong-way drivers on highways, including those driving the wrong way on highway ramps, according to the Turner-Fairbank Highway Research Center (TFHRC). (TFHRC is a federally owned and operated research facility in McLean, Virginia that is associated with the U.S. Department of Transportation Federal Highway Administration's (FHWA) Office of Research, Development, and Technology.) These statistics are based on an analysis of data from the National Highway Traffic Safety Administration's Fatal Accident Reporting system (FARS).

Connecticut averages about nine wrong-way accidents on its interstate highway system annually, according to the Connecticut Department of Transportation. A review of Connecticut accident data on FARS shows there were three wrong-way accidents involving a fatality in 2004, five in 2005, and two in 2006. (This is the most recent data available on FARS.) None of the accident reports indicate if an improper entry to or exit from the roadway was a related factor in the incident.

Before 2002, the majority of research related to wrong-way driving on highways was done in the late 1960s to late 1970s, primarily in California, Georgia, and Washington. In cooperation with the FHWA, and as a result of numerous crashes in Texas' Fort Worth area from 1997 to 2000, the Texas Department of Transportation sponsored a research project by the Texas Transportation Institute (TTI) to identify effective wrong-way driving countermeasures to reduce the frequency and severity of accidents caused when drivers enter highways in the wrong way. (TTI is a transportation research agency affiliated with the Texas A&M University System.)

TTI's research resulted in a report that provides guidelines and recommended practices, as well as a checklist for road construction engineers and crews to use when reviewing wrong-way entry issues or problem locations. A summary is provided in Countermeasures for Wrong-Way Movement on Freeways: Guidelines and Recommended Practices (Research Report 0-4128-2, Texas Transportation Institute, Texas A&M University System, January 2004, available at; copy enclosed).

TTI reviewed published studies, conducted Internet searches, and surveyed 50 state Departments of Transportation (DOTs), 28 of which responded (including Connecticut), to gather information on wrong-way driving countermeasures. It determined that there are four basic categories of countermeasures:

1. traditional signing and pavement marking techniques,

2. innovative signing and pavement marking techniques,

3. geometric modifications (e.g., ramp and road design changes), and

4. intelligent transportation system (ITS) applications.

TTI's guidelines include:

1. installing and maintaining reflective and raised wrong-way pavement arrow markers on exit ramps, particularly at left-side exits, newly constructed ramps, and locations with a history of wrong-way accidents;

2. mounting DO NOT ENTER and WRONG WAY signs mounted on the same post and at a lower height than usual (lowered signs may be easier to see when driving impaired or at night); and

3. installing inductive loops or other detectors in exit ramps under construction, allowing for wrong-way detection and warning systems. (An inductive loop is a coil of wire embedded in the road's surface that detects when a car is on the road by a change in the electromagnetic current of the device.)

The U.S. DOT is researching ITS applications and intelligent vehicle designs that could warn drivers of hazards, as is the auto industry. California, Florida, New Mexico, and Washington have experimented with ITS for wrong-way driving, and recently Texas has installed the technology on Houston's new Westpark Tollway.


Traditional methods for preventing wrong-way driving on highways include:

1. DO NOT ENTER and WRONG WAY signs on separate posts,

2. oversized DO NOT ENTER and WRONG WAY signs,

3. red reflective raised pavement markers on the main lanes of the highway or ramp to delineate roadways that must not be entered or used,

4. wrong-way pavement arrows,

5. yellow edge line on the left side and white edge lines on the right side of exit ramps,

6. ONE WAY signs, and

7. turn restriction signs (e.g., symbol or text signs indicating no left turn and no right turn).

Most Departments of Transportation (DOTs) use traditional signing and pavement marking techniques, following the standards, guidance, and options the FHWA provides in its Manual on Uniform Traffic Control Devices (2003 edition with Revisions 1 and 2 Incorporated, dated December 2007) (MUTCD). The MUTCD is written in terms of shall, should, and may to identify requirements, recommendations, and suggestions for the states.


TTI found that 97% of the 28 DOTs that responded to its survey use DO NOT ENTER and WRONG WAY signs. The MUTCD includes the following regarding DO NOT ENTER signs:

Standard: The DO NOT ENTER sign shall be used where traffic is prohibited from entering a restricted roadway.

Guidance: The DO NOT ENTER sign, if used, should be placed directly in view of a road user at the point where a road user could wrongly enter a divided highway, one-way roadway, or ramp. The sign should be mounted on the right side of the roadway, facing traffic that might enter the roadway or ramp in the wrong direction. If the DO NOT ENTER sign would be visible to traffic to which it does not apply, the sign should be turned away from, or shielded from, the view of that traffic.

Option: The DO NOT ENTER sign may be installed where it is necessary to emphasize the one-way traffic movement on a ramp or turning lane. A second DO NOT ENTER sign on the left side of the roadway may be used, particularly where traffic approaches from an intersecting roadway.

For WRONG WAY signs, the MUTCD instructs:

Option: The WRONG WAY sign may be used as a supplement to the DO NOT ENTER sign where an exit ramp intersects a crossroad or a crossroad intersects a one-way roadway in a manner that does not physically discourage or prevent wrong-way entry.

Guidance: If used, the WRONG WAY sign should be placed at a location along the exit ramp or the one-way roadway farther from the crossroad than the DO NOT ENTER sign.

The MUTCD shows the above guidance in Figure 2B-10, copied below.

Full-size image of Figure 2B-10

Pavement Arrows

Wrong-way pavement arrows are another traditional countermeasure for discouraging wrong-way entry onto restricted facilities. But TTI found that only 24% of the DOTs responding to its survey use wrong-way pavement arrows on all exit ramps; 28% use them on known or suspected problem areas.

Section 3B of the MUTCD provides the following advice for pavement markers, including the optional use of wrong-way pavement arrows:

Standard: Where through traffic lanes approaching an intersection become mandatory turn lanes, lane-use arrow markings shall be used and shall be accompanied by standard signs. (See MUTCD Figure 3B-21-b below for one example.)

Guidance: Where crossroad channelization or ramp geometrics do not make wrong-way movements difficult, a lane-use arrow should be placed in each lane of an exit ramp near the crossroad terminal where it will be clearly visible to a potential wrong-way road user.

Option: Wrong-way arrow markings (23.5 feet in length) may be placed near the downstream terminus of a ramp to indicate the correct direction of traffic flow and to discourage drivers from traveling in the wrong direction. (See MUTCD Figure 3B-21-d below.)

Red Reflective Raised Pavement Markers

Some DOTs use red reflective raised pavement markers on highway lanes and exit ramps along the road edge, as part of a wrong-way pavement arrow (see MUTCD Figure 3B-21-e above), or both. TTI found that 38% of DOTs responding to its survey use them on highway lanes as a standard practice.

A standard red raised pavement marker, which is placed with the red side facing the wrong-way direction, is pictured in Figure 1.

Figure 1: Red Raised Pavement Marker

Source: Countermeasures for Wrong-Way Movement on Freeways: Guidelines and Recommended Practices, Texas Transportation Institute, January 2004.


Innovative signing and pavement marking techniques for preventing wrong-way driving on highways include:

1. DO NOT ENTER and WRONG WAY signs that are mounted lower than the standard MUTCD sign height and on the same post;

2. DO NOT ENTER and WRONG WAY signs that are supplemented with (a) additional signs (e.g., FREEWAY, ONE WAY, or RAMP), (b) flashing lights, or (c) internal illumination;

3. GO BACK YOU ARE GOING THE WRONG WAY signs (60 inches by 36 inches);

4. non-standard wrong-way pavement arrows (e.g., oversized);

5. red reflective tape on the backs of highway signs;

6. extra overhead lighting; and

7. red delineators on each side of the ramp up to the WRONG WAY sign.

Lower Sign Mounting Height

The MUTCD identifies the standard mounting height for road signs (i.e., the distance from the ground to the bottom edge of the sign) as seven feet in urban areas and five feet in rural areas. TTI found that about 86% of the 28 DOTs that responded to its survey follow the standard mounting height for WRONG WAY signs.

According to the TTI, lowering the mounting height of DO NOT ENTER and WRONG WAY signs may be an effective countermeasure for preventing wrong-way entries onto highways. The studies TTI reviewed indicate that a lower mounting height makes the signs more visible (1) at night because lower signs are in the path of a car's headlights and (2) to impaired and older drivers who tend to drive with their eyes low looking for visual cues from the pavement area.

California. In 1973, California implemented sign standards that differ from the MUTCD, including lowered DO NOT ENTER and WRONG WAY signs mounted together on the same post. The decision to do so was based on studies its DOT (Caltrans) conducted. Caltrans has found that before it introduced its sign standards, some locations had 50 to 60 wrong-way entries at off ramps each month. After the new sign standards were implemented, the number of wrong-way entries at off ramps dropped to two to six each month in 90% of the problem areas.

Caltrans' sign standards include:

1. Placing the bottom of the DO NOT ENTER and WRONG WAY sign package two feet above the pavement. (See Figure 2 below.)

2. Mounting ONE WAY arrows one and a half feet above the pavement. (See Figure 3 below.)

3. Placing at least one DO NOT ENTER and WRONG WAY sign package to fall within the area covered by a car's headlights and visible to the driver from the decision point on each likely wrong-way approach.

4. Installing FREEWAY ENTRANCE signs as near to the on ramp and cross street intersection as possible.

5. Not using symbol right or left turn prohibition signs at ramps because of possible misunderstandings by impaired drivers as directional arrows; word signs may be used. (See Figure 3 below.)

Georgia and Virginia. Georgia and Virginia each use lowered DO NOT ENTER and WRONG WAY signs mounted together as standard practice. Each adopted California's standard sign criteria at off-ramps after conducting their own studies in 1979 and 1980, respectively. Georgia also uses a 24-inch wide painted stop bar at the crossroad end of the ramp.

Figure 2: Lowered DO NOT ENTER and WRONG WAY Sign Package in California

Source: Countermeasures for Wrong-Way Movement on Freeways: Guidelines and Recommended Practices, Texas Transportation Institute, January 2004.

Figure 3: Lowered ONE WAY and Turn Restriction Signs in California

Source: Countermeasures for Wrong-Way Movement on Freeways: Guidelines and Recommended Practices, Texas Transportation Institute, January 2004.

Supplemental Signs

In some cases, DOTs supplement the standard (or lowered, combined) DO NOT ENTER and WRONG WAY signs with additional measures, such as using oversized signs or additional signs (e.g., RAMP, FREEWAY) or a second wrong-way pavement marker further along the ramp.

Ohio. In 2005, Ohio installed additional signs on ramps that had the potential for wrong-way movement. The typical layout uses enhanced red background signs installed in pairs (i.e., one on each side of the road), as follows:

1. DO NOT ENTER signs at the ramp throat;

2. double WRONG WAY signs part-way down the ramp (i.e., two WRONG WAY signs mounted on the same post, the bottom sign mounted at one foot above the pavement); and

3. DO NOT ENTER and WRONG WAY signs further along the ramp closer to the highway (i.e., both are mounted on the same post where the DO NOT ENTER sign is above a low-mounted WRONG WAY sign).

Ohio also affixed red reflective tape to the sign posts to enhance nighttime visibility. (Source: NCHRP Report 500: Guidance for Implementation of the AASHTO Strategic Highway Safety Plan, Volume 20: A Guide for Reducing Head-On Crashes on Freeways, National Cooperative Highway Research Program, Transportation Research Board, Washington, D.C., 2008, p. V-34.) (AASHTO is the American Association of State Highway and Transportation Officials.)

Flashing Lights and Internally-Illuminated Signs

When TTI conducted its study of DOTs, it found that one responder uses a “flasher assembly” to draw attention to the DO NOT ENTER or WRONG WAY signs. A “flasher assembly” is typically a blinking red light attached to the sign. And TTI found that 10% of DOTs responding use internally-illuminated signs (i.e., signs the light up from the inside).


Several studies have shown that certain interchange designs are more susceptible to wrong-way movements than others and identified a number of modifications to limit such movement.

Interchange Design

The NCHRP Report 500 indicates that a full-diamond interchange is the most common design. As a result, the NCHRP believes a full-diamond ramp design minimizes driver confusion and, thus, wrong-way movement. A 1989 Caltrans study, Prevention of Wrong-Way Accidents on Freeways (Report No. FHWA/CA-TE-89-2) found that the full-diamond design, though good, still lends itself to confusion and recommends proper signage, directional arrows, and pavement markers to guide drivers.

The Caltrans study found that a full-cloverleaf interchange is the most desirable for preventing wrong-way movement. Caltrans also found that trumpet and buttonhook ramps are the most susceptible to wrong-way driving. Examples of various designs are shown in Figures 4 though 7 below.

Washington state conducted a 10-year study from 1986 to 1996 of an 80-mile section of I-82 that revealed 30 wrong-way crashes along the corridor. The study found that the most probable wrong-way entry location was a partial-cloverleaf interchange at I-82 and Highway 22 (i.e., looping ramps separated by concrete barriers that drivers could not see around). Then from May to December 2001, camera monitors recorded 18 wrong-way incidents at this location. As a result, the Washington DOT removed stretches of the barriers at that and similar interchanges in the South Central Region to provide drivers with better visibility of on-ramps.

The FHWA discourages the use of isolated off-ramps because they have historically resulted in a higher than normal frequency of wrong-way moves onto the freeway.

(Source of images: Steve Moler, Stop. You're Going the Wrong Way!, Public Roads, September/October 2002.)

Figure 4: Full-Diamond Interchange

Diagram of full diamond interchange

Figure 5: Full-Cloverleaf Interchange

Diagram of full cloverleaf interchange

Figure 6: Trumpet Interchange

Diagram of trumpet interchanges

Figure 7: Buttonhook Ramps

Diagram of buttonhook ramps

Geometric Modifications as Countermeasures

TTI noted two main modifications in roadway geometry used as wrong-way driving countermeasures: (1) offsetting entrance and exit ramps and (2) reducing the size of the off-ramp “throat” so that the opening is less inviting to a potential wrong-way driver.

Other possible modifications include (1) channeling the off-ramp traffic in one direction only so that a potential wrong-way driver is presented with an entry barricade (e.g., curbing); (2) where on- and off-ramps are adjacent on a combined paved surface, add delineators or painted islands as separators; and using sharp turns (i.e., small radii corners) at an exit ramp throat. (Sources: NCHRP Report 500 and FHWA's May 2001 Highway Design Handbook for Older Drivers and Pedestrians.)


Federal Initiatives

According to the U.S. DOT, intelligent transportation systems, or ITS, “improves transportation safety and mobility and enhances American productivity through the integration of advanced communications technologies into the transportation infrastructure and in vehicles. ITS encompass a broad range of wireless and wire line communications-based information and electronics technologies.” (See

At the federal level, the U.S. DOT's Research and Innovative Technology Administration (RITA) is researching ITS applications that focus on both the transportation infrastructure and vehicles, as well as integrated applications between the two.  Common ITS technologies used today include electronic toll collection, in-vehicle navigation systems, rear-end collision avoidance systems, and dynamic message signs.  RITA's National ITS Architecture and Standards program provides states a framework for interoperable ITS systems (i.e., those that can exchange information) and training on the latest ITS applications developed.

Among the numerous ITS initiatives RITA is studying is intersection collision avoidance systems. Intersection collision avoidance systems use both vehicle-based and infrastructure-based technologies to help drivers approaching an intersection understand what is occurring within that intersection. Cooperative intersection collision avoidance systems (CICAS) could warn drivers about vehicles going through red-lights and

other possible traffic violations to help them maneuver safely through the intersection. RITA hopes that CICAS may also inform drivers of pedestrians and cyclists within an intersection.

CICAS consists of:

1. vehicle-based technologies and systems: sensors, processors, and driver interfaces within each vehicle;

2. infrastructure-based technologies and systems: roadside sensors and processors to detect vehicles and identify hazards and messaging signs or other interfaces to communicate warnings to drivers; and

3. communications systems: dedicated short-range communications to communicate warnings and data between the infrastructure and equipped vehicles.

Private Initiatives

BMW, as well as other automakers, are working to make vehicles more intelligent. For example, using the car's navigation system, BMW has developed a wrong-way driver information system that recognizes when a driver is about to enter a roadway in the wrong direction. The system triggers a warning, both audible and visual, to alert the driver. BMW is engineering the system to “speak” to other vehicles to warn other drivers that a wrong-way driver is approaching. In addition to vehicle-to-vehicle communication systems, BMW is developing vehicle-to-infrastructure communication systems. (

State Initiatives

California, Florida, New Mexico, and Washington are among the states that have made the most use of ITS applications with respect to wrong-way drivers. Most recently, Texas has installed inductive loop technology on Houston's new Westpark Tollway following several wrong-way crashes that resulted in multiple fatalities, according to a presentation TTI made at the Transportation Research Board's January 2008 annual meeting.


Vehicle-Infrastructure Integration (VII). U.S. DOT's Information Technology Services' Joint Program Office has recognized Caltrans for its innovation and leadership in transportation technology by officially including Vehicle-Infrastructure Integration (VII) California into the national ITS efforts. Caltrans and the Bay Area Metropolitan Transportation Commission (MTC) have each committed $1.5 million to conduct research on VII. Caltrans is the first U.S. public agency to install VII “hot spots.”

According to Caltrans' “Strategic Plan 2007-2012,” Caltrans and the MTC are developing a 60-mile testbed where VII is being tried in partnership with the auto industry and the University of California, Berkeley. If VII were implemented, every U.S. manufactured car would be equipped with a communications device and a global positioning system (GPS) so that data could be exchanged with a nationwide, instrumented roadway system.

Data transmitted between dedicated short-range communication units along the roads and vehicles could warn a driver of impending dangers. The VII California testbed consists of three parallel routes on the state highway system: US-101, SR-82 (El Camino Real), and I-280. The end points for the testbed are roughly SR-92 in the north and SR-85 in the south, making it about twenty miles in length. A primary consideration for choosing this corridor is its close proximity to the Palo Alto area, since four of the auto industry partners (BMW, DaimlerChrysler, Toyota, and VW/Audi) have research facilities there, where they are performing vehicle development work and stage tests using the VII California testbed.

In-Pavement Warning Lights. TTI notes that California has used in-pavement warning lights as a wrong-way driving countermeasure on exit ramps prone to wrong-way incidents. When a wrong-way vehicle drives over an inductive loop detector, it activates a series of warning lights imbedded in the pavement alerting the driver that he or she has entered an off-ramp or other restricted roadway. (An inductive loop is a coil of wire embedded in the road's surface that detects when a car is on the road by a change in the electromagnetic current.) Figure 8 is a picture of in-pavement warning lights for wrong-way vehicles.

Figure 8: In-Pavement Warning Lights for Wrong-Way Vehicle

Source: Countermeasures for Wrong-Way Movement on Freeways: Guidelines and Recommended Practices, Texas Transportation Institute, January 2004.

Florida: Wrong-Way Detection and Warning System on Bridge

Florida installed a wrong-way driver detection and warning system on a bridge that was the site of several fatal wrong-way crashes. When loop detectors in the roadway detect a wrong-way driver, the system activates flashing lights on wires spanning the bridge overhead to warn oncoming motorists. At the same time, according to TTI,it automatically notifies a nearby police substation of the incident.

New Mexico: Directional Traffic Sensor System

According to TTI, New Mexico installed a directional traffic sensor system (DTSS) in 1998 at an exit ramp of I-40 to detect wrong-way movement and alert oncoming traffic. The DTSS uses inductive loop sensors to detect the wrong-way movement. This activates two sets of warning lights that flash for one minute each.

A set of red flashing lights mounted on a traditional WRONG WAY sign faces the wrong-way driver. On the back of this sign, a set of yellow flashing lights mounted on a STOP AHEAD sign faces the driver moving in the correct direction. When the yellow lights flash, it alerts an oncoming car of potential danger ahead. TTI indicates that the DTSS is designed to be effective in bad weather and with disoriented drivers. Figure 9 provides an illustration of the DTSS.

In 2006, New Mexico experimented with solar-powered flashing lights, but Robert Ortiz, DOT Deputy Secretary, said the lights did not perform well when the solar panels were dirty. (D. Collins, “Working to Keep Drivers on the Right Side: State tries various methods to warn wrong-way motorist,” Santa Fe New Mexican, October 25, 2007.)

Figure 9: New Mexico Directional Traffic Sensor System

Source: Countermeasures for Wrong-Way Movement on Freeways: Guidelines and Recommended Practices, Texas Transportation Institute, January 2004.

Washington: Wrong-Way ITS System

Washington has experimented with solar-powered and traditional-powered vehicle detection systems that use flashing lights, electronic LED (light emitting diode) signs, and video cameras. A wrong-way vehicle triggers the system, turning on a red WRONG WAY electronic LED sign, flashing lights, and video camera, which records the incident for further evaluation. The NCHRP Report 500 notes that in both the solar- and traditional-powered systems, Washington's ITS system was “plagued with maintenance problems.” Figure 10 pictures Washington's system.

Figure 10: Washington State Wrong-Way ITS System

Source: Countermeasures for Wrong-Way Movement on Freeways: Guidelines and Recommended Practices, Texas Transportation Institute, January 2004.