Radar Speed Signs: Do They Issue Tickets?

By I Go Cars · Updated October 29, 2026

Radar speed signs do not issue tickets

Radar speed signs do not issue tickets. The Iowa Department of Transportation states that its signs "do not store data and do not conduct radar enforcement or result in automated speed violation tickets/citations." Clackamas County, Oregon, says its signs "do not issue citations, take photographs, or collect license plate or personal information." A radar speed sign, also called a driver feedback sign or dynamic speed display sign, is a traffic-calming device: it measures the speed of an approaching vehicle and shows that speed to the driver, nothing more.

Iowa DOT's definition is the plainest available: "A speed feedback sign measures the speed of approaching vehicles and displays the speed on a digital sign." The purpose is feedback. A driver who sees a number above the posted limit gets an immediate, impersonal reminder, without a stop or a fine.

The distinction from automated enforcement matters. A speed safety camera is a different device, authorized separately by law, that records a violation and leads to a citation. A feedback sign mounted on a pole, or towed on a trailer, does neither. Whether a jurisdiction anywhere in the United States links a feedback sign to a citation camera was not established by any official source located for this page.

Names, data collection and who makes them

The same device carries several names in official documents. The Federal Highway Administration (FHWA) uses "dynamic speed feedback signs." The Texas A&M Transportation Institute (TTI), working for the Texas Department of Transportation, and Morgan State University use "dynamic speed display signs," abbreviated DSDS. The federal Manual on Uniform Traffic Control Devices (MUTCD), the national standard for road signs, uses "Vehicle Speed Feedback Sign" (code W13-20) and "Vehicle Speed Feedback plaque" (W13-20aP).

Data collection depends on the program, not on the technology. Iowa DOT's signs store no data. Clackamas County's signs may log anonymous speed and traffic volume figures for engineering use. Neither collects license plates.

The 2008 NHTSA and FHWA Speed Enforcement Program Guidelines (DOT HS 810 915) describe "SMART trailers and speed reader boards" as speed measurement devices used to raise driver awareness. The guidelines give no measured effect and note that publicity alone has a mild effect and is more effective when paired with enforcement.

Several companies that make police radar also make feedback signs and trailers, including Kustom Signals (PMD signs and SMART trailers), MPH Industries (Speed Guardian and Speed Monitor), Applied Concepts under its Stalker Street Dynamics brand, and Decatur Electronics. A New York State purchasing contract also lists All Traffic Solutions and Traffic Logix. These names are recorded as fact; this site does not compare or rate them.

Do feedback signs slow drivers? Rural curves

The largest federal study found consistent, modest reductions that lasted. FHWA's national demonstration, published January 2015 as FHWA-HRT-14-020 (Hallmark, Hawkins and Smadi), placed dynamic speed feedback signs at 22 sites on rural two-lane curves in seven states: Arizona, Florida, Iowa, Ohio, Oregon, Texas and Washington.

Mean speed: at the point of curvature (where the curve begins), average reductions across all sites were 1.82 mph after one month, 2.57 mph after 12 months and 1.97 mph after 24 months.
Center of the curve: 2.08, 1.65 and 1.76 mph at the same intervals.
Fast drivers: the share of vehicles traveling 10 mph or more over the posted or advisory speed at the point of curvature fell by 29.9 percent at one month, 34.4 percent at 12 months and 29.3 percent at 24 months.
Individual sites: mean speed decreases reached up to 10.9 mph.
Crashes: crash modification factors (multipliers estimating the change in expected crashes; 0.95 means about 5 percent fewer) ranged from 0.93 to 0.95 depending on crash type and direction.

The study found no statistically significant change in the effect across one, 12 and 24 months. Its 24-month data covered 18 of the 22 sites, because four signs had stopped working. FHWA's Crash Modification Factors Clearinghouse lists the study with factors of 0.95 for all crashes, 0.93 for all crashes in a second analysis, and 0.95 for single-vehicle crashes. The full report is available from FHWA.

School zones, intersections and city streets

Other studies show that results depend heavily on the site.

Texas, 2004

TTI's study of permanent dynamic speed display signs (report 0-4475-S, January 2004, Ullman and Rose) found its largest effect in a school speed zone. Drivers there had been traveling nearly 10 mph over the limit. After installation, average speeds fell by more than 9 mph and were still 9 mph lower four months later. Elsewhere the picture was mixed:

A school transition zone saw a 3 mph reduction at first and 1 to 2 mph after four months.
One signalized intersection saw 3 mph at first, then a return to pre-installation speeds by four months.
Another signalized intersection saw a 4 mph reduction that was sustained.
Sharp horizontal curves showed "little change."

Baltimore, 2012

A Morgan State University National Transportation Center study (September 2012, Jeihani, Ardeshiri and Naeeni) measured reductions next to the sign of about 2.9 mph on a 35 mph road, about 0.5 mph on a 45 mph road and about 0.2 mph in a 25 mph school zone. The effect held "for a very short distance"; speeds 900 feet downstream were higher. The probability of driving below the limit fell from 31.2 percent in the first two days to 9.9 percent after 12 or more days. The authors concluded that "a DSDS should be used as a temporary solution because its effectiveness reduces with time."

A survey in the same study is revealing, though it was a convenience sample of 88 respondents: 63 percent said they slowed mainly to avoid a ticket, and 48 percent said they would speed up if the sign showed them under the limit.

What the MUTCD requires

The MUTCD 11th Edition (December 2023) treats feedback signs in Section 2C.13. Their use is optional: a W13-20 sign or W13-20aP plaque "that displays the speed of an approaching vehicle to the vehicle operator may be used to provide warning to drivers of their speed in relation to either a speed limit (R2-1) sign or a horizontal alignment warning sign assembly with a posted advisory speed." Once used, the standards are mandatory:

Placement: with a speed limit, the plaque "shall be mounted below a Speed Limit (R2-1) sign"; at a curve, the sign "shall be an independent installation near the point of curvature."
Colors: "YOUR SPEED shall be a black legend on a yellow retroreflective background," with exceptions for work zones and school areas in Sections 6H.01 and 7B.01; the changing speed "shall be a yellow luminous legend on a black opaque background."
Display: the speed is shown "as an integer," and the sign and plaque "shall not flash, strobe, change color, or use other animated elements integrated into the changeable legend display."
Idle state: "When no vehicles are approaching, the changeable display shall not display a legend."

Guidance in the same section calls for digits about the same height, width and stroke as those on the Speed Limit sign, and a plaque about the same width. An earlier FHWA interpretation (July 15, 2010) had already reserved amber or yellow LEDs for the approach-speed display, with white for changeable Speed Limit legends. Flashing or color-changing "SLOW DOWN" displays therefore do not conform to the current manual. The text is in MUTCD Chapter 2C.

What people get wrong about feedback signs

"The sign photographed my plate." Iowa DOT and Clackamas County state their signs issue no citations, and Clackamas says its signs take no photographs or plate data.
"They work forever." Results vary: FHWA's curve signs held their effect for 24 months, TTI's sites ranged from sustained to fully reverted, and Morgan State found effects fading within about two weeks.
"They work everywhere." The documented effects are strongest in school zones and on rural curves, and weakest on sharp curves with competing warnings and on a higher-speed multilane road.

Programs are also finite. Iowa DOT funds signs on state highways in incorporated cities of 750 to 15,000 people at about $750,000 a year; installations began in July 2023, and new locations are on hold until at least July 1, 2027, according to the department.

Frequently asked questions

Do radar speed signs give tickets?

No. Radar speed signs display a driver's speed and do not issue tickets. Iowa DOT states its signs do not result in automated speed violation tickets or citations, and Clackamas County, Oregon, says its signs take no photographs and collect no license plate or personal information. A speed safety camera is a separate, separately authorized device.

Do driver feedback signs actually slow people down?

Yes, usually by a few miles per hour, though results depend on the site. FHWA's 22-site study of rural curves found average reductions of about 2 mph sustained over 24 months and crash modification factors of 0.93 to 0.95. TTI found more than 9 mph in a Texas school zone; Morgan State found effects fading within about two weeks.

Do speed feedback signs record data?

It depends on the program. Iowa DOT's signs store no data at all. Clackamas County, Oregon, says its signs may log anonymous speed and traffic volume figures but take no photographs and collect no license plate or personal information. The data function is a choice made by the operating agency.

Why don't speed feedback signs flash anymore?

The MUTCD 11th Edition, issued in December 2023, prohibits it. Section 2C.13 states that the feedback sign and plaque shall not flash, strobe, change color or use other animated elements in the changeable display. The speed must appear as a yellow integer on a black background and go blank when no vehicle is approaching.

What color are speed feedback sign numbers supposed to be?

Yellow on black. The MUTCD 11th Edition requires the changeable speed to be a yellow luminous legend on a black opaque background, while the YOUR SPEED legend is black on a yellow retroreflective background, with exceptions for work zones and school areas. FHWA's 2010 interpretation had already reserved amber or yellow LEDs for the approach-speed display.

How long do radar speed signs stay effective?

Studies disagree, because effects depend on the site. FHWA found no significant decline over 24 months on rural curves. TTI found a school-zone reduction of 9 mph still in place after four months, while one intersection returned to its original speeds. Morgan State found the effect fading within about 12 days and called the signs a temporary measure.

Radar speed signs: what they do and what the evidence shows