A Purple Alert on a highway sign means law enforcement is searching for a missing adult who has a cognitive, intellectual, or developmental disability and is believed to be in danger. The sign shows a vehicle make, model, color, and license plate, and sometimes a brief physical description of the missing person. If you see one, read it carefully and call 911 if you spot the vehicle.
What the Sign Is Telling You
Purple Alerts cover a specific group: adults 18 and older with a qualifying disability whose disappearance suggests real danger. Qualifying conditions generally include an intellectual or developmental disability, a brain injury, or another physical, mental, or emotional disability. Psychiatric conditions like schizophrenia or bipolar disorder can qualify on their own.
Two groups are deliberately excluded. Alzheimer’s and other dementias fall under Silver Alerts, not Purple. Disabilities tied to substance abuse are also excluded.
The highway display itself is compressed to the essentials. You’ll typically see “PURPLE ALERT” at the top, then the vehicle details and plate. Some signs cycle through a short physical description. The signs usually stay active for a limited window, often around six hours, to keep the information timely.
Not every Purple Alert reaches the signs. When the missing person left on foot or in an unidentified vehicle, there’s no plate to display, and local law enforcement distributes the alert through media and officer-to-officer channels instead. Highway sign activation generally requires an identified vehicle with a confirmed plate.
What To Do If You See One
Read the sign. That sounds obvious, but most drivers glance at message boards without absorbing anything. Take a mental snapshot of the vehicle description and plate number.
If you spot a matching vehicle, call 911 right away. Tell the dispatcher your exact location, the direction the vehicle is heading, and anything else you noticed, like the number of people inside or which exit it took.
Do not try to follow the vehicle or approach the missing person yourself. People with these conditions can find unexpected contact with strangers frightening or disorienting, and a well-meaning intervention can escalate the situation. Let trained responders handle the approach.
The same rules apply if you receive a Purple Alert through a text-based emergency notification or on local radio or television: observe, remember details, call 911 if you see a match.
How Purple Alerts Compare to AMBER and Silver Alerts
Highway alert systems split missing persons by age and condition, and the categories don’t overlap much.
- AMBER Alerts cover missing children under 18, usually when abduction is suspected and the child faces risk of serious injury or death.
- Silver Alerts cover older adults, generally 60 and above, with Alzheimer’s, dementia, or similar cognitive deterioration. Some states extend them to younger adults who are mentally incapable of caring for themselves, but the core focus is age-related cognitive decline.
- Purple Alerts cover adults 18 and older with disabilities that are not dementia-related. A 30-year-old with autism or a 45-year-old with a traumatic brain injury who wanders from home fits here. Before Purple Alerts existed, these cases didn’t qualify for any highway alert.
At the federal level, the Ashanti Alert Act of 2018 directed the Department of Justice to establish a national communications network for missing adults between 18 and 64, but it left individual states to build and name their own programs.1Congress.gov. H.R.5075 – Ashanti Alert Act of 2018
How a Purple Alert Gets Issued
Families cannot issue Purple Alerts directly. The process starts with a missing person report to local law enforcement, and one point worth stating plainly: there is no mandatory waiting period to report someone missing. The “wait 24 hours” idea is a myth, and it’s especially harmful when a vulnerable adult is involved. Call police as soon as you believe the person is gone.
Once the report is filed, officers evaluate whether the case meets Purple Alert criteria: a qualifying disability, circumstances suggesting danger, and enough descriptive information to make an alert useful. If it qualifies, the local agency requests activation from the state’s missing persons clearinghouse, usually housed within the state law enforcement agency.
Speed depends on what information is ready. A recent photo, a detailed physical description, known clothing, and a vehicle with a plate number all move things faster.
Preparing Before Something Happens
If you care for someone who could one day be the subject of a Purple Alert, prepare now rather than during a crisis. Some law enforcement agencies run voluntary vulnerable person registries that let families pre-load key information: a current photograph, physical description, behavioral triggers, medical conditions, medications, and calming techniques that work for that individual. When a disappearance is reported, dispatchers and officers can pull up the record immediately instead of gathering it from a distraught family member.2COPS Office (U.S. Department of Justice). Vulnerable Person Registries: Reimagining Crisis Response
In agencies that use them, the registry data is integrated with dispatch so responding officers see the person’s photo, interests, and behavioral notes before arriving. Officers describe the pre-loaded calming and trigger information as effective for building rapport during encounters.2COPS Office (U.S. Department of Justice). Vulnerable Person Registries: Reimagining Crisis Response
Not every agency offers a formal registry, but you can still get ready. Keep an updated file with a recent photo, physical description, medical information, and behavioral notes. Know the person’s typical wandering patterns and favorite destinations. If they carry a phone, enable location sharing. None of this guarantees a faster Purple Alert, but it gives law enforcement something concrete to use in the first hours, which matter most.
Where Purple Alerts Exist
Purple Alerts are not nationwide. As of early 2025, roughly half a dozen states have enacted Purple Alert legislation, with more considering it. Each state built its program through its own legislation, so eligibility criteria, activation procedures, and distribution methods vary. The core idea is the same everywhere: locate missing adults with disabilities who don’t qualify for Silver or AMBER Alerts.
You may drive through states that have Purple Alerts and others that don’t. In states without one, missing vulnerable adults are still reported through standard missing person channels, but there’s no dedicated highway-sign and mass-notification infrastructure behind the search.