Tailgating vs piggybacking.
Tailgating is an unauthorized person slipping through a controlled door behind someone who badged in, without that person’s knowledge or agreement. Piggybacking is the same entry with the badge holder’s consent: holding the door for a delivery driver, letting in a coworker who forgot their card, waving through a “visitor”. The access control system sees the same thing in both cases: one valid credential and one door opening. Everything else happens in the doorway, and only a camera sees it.
It matters most where the door is the security: data center cages and mantraps, office and campus lobbies and side doors, apartment entrances and garages, hospital staff corridors, and loading docks.
What cameras can actually show.
A well-placed door camera can show how many people passed through, in which direction, and whether they came together or one followed the other. It can show a door propped with a wedge, held open for a stranger, or reopened from inside moments after a badge-in. It shows what the badge reader does not: who actually walked through.
Placement decides whether any of that is visible:
- Look at the approach, not the door. A view down onto the threshold that includes a few steps on the secure side shows people separating as they enter.
- Avoid pure backlight. Glass entrance doors facing daylight turn people into silhouettes that merge together. Angle the camera or adjust exposure for the door.
- Cover both sides where it matters. Outside shows who approached; inside shows how many actually entered.
- Keep the reader in frame. Seeing the badge tap makes it clear which person used the credential.
What cameras cannot do alone is know how many people were authorized. That information lives in the access control system.
Combine video with access control events.
The strongest tailgating process pairs the two sources. Access control says who badged, when and at which door; video says how many people went through and what happened. Guards and investigators use that combination in three ways:
- Door forced and door held alarms. Most access systems already raise these. Each one should come with a look at the camera at that moment, not just an acknowledgement.
- Badge event review. For sensitive doors, the guard checks the video for a sample of badge-ins, or all of them after hours: one badge, one person.
- Investigations. After an incident, the badge log narrows the time; the video shows who followed whom.
Some integrated platforms count people crossing a line and compare that with badge grants automatically. That is powerful where the door, the camera and the access system are from vendors that work together. Many guard companies and monitoring centers do not have that luxury: the access system and the cameras are separate, owned by the client and different at every site.
What guards should do about it.
Know which doors matter
List the doors where one person per badge is required and the hours it applies. Put them on the monitoring wall first.
Review the moments
For every held-door, forced-door or after-hours entry, look at the video: how many people, together or following, and where did they go?
Respond by policy
A friendly challenge, a call to the site, a patrol or police. Log it with the frames and the badge event side by side.
Most tailgating is social, not criminal: politeness beats policy at the door. Repeat patterns belong in a report to the client so they can fix the behavior, the door hardware or the post orders.
Where Semaphor fits.
Semaphor does not replace access control and does not read badges. It watches the entrance cameras on the monitoring screen your team already uses — no integration project with the door vendor or the VMS; see what Semaphor is. Person detection at entrances puts people at a controlled door in front of the guard, with numbered per-camera tracks so two people coming through show up as two, and the original frames attached. After hours, when anyone at the door is worth a look, that is exactly the alert you want.
The guard compares it with the access control event and decides. That is guard review by design: the AI surfaces the doorway, the human applies the policy. Want to see it on your entrances? Contact us for a live demo on your own camera screens, or start a pilot.
Tailgating FAQ
What is the difference between tailgating and piggybacking?
Tailgating is following an authorized person through a door without their knowledge. Piggybacking is the same entry with their consent, like holding the door. Both defeat one-person-per-credential rules.
Can security cameras detect tailgating?
Cameras can show how many people passed through a door and how. Automatic tailgating alarms also need the access control event to know how many entries were authorized, or a guard who checks both.
Where should a camera be placed to catch tailgating?
Looking down on the threshold with a view of a few steps inside the secure side and the reader in frame. Avoid shooting straight into bright glass doors.
Does Semaphor integrate with our access control system?
No integration is required. Semaphor works from the camera screens and surfaces people at entrances; guards pair that with the access events they already see.