In Part I of this two-part article, “Defining Basic Tailgating Prevention Capabilities and Goals,” we organized different types of pedestrian security entrances into four distinct Capability Levels for combatting tailgating: Crowd Control, Deterrent, Detection and Prevention. We showed that each level has a different impact on an organization in terms of capital cost and whether security staff are recommended based on the entrance location and the need to respond to jumping over, crawling under, or other tailgating infractions.

In Part II, we’ll dig deeper into each Capability Level to determine the potential for measuring success and ROI. The table above has been expanded to show other factors: Throughput, Metrics Capability, Recommended User Education, Annual Operating Costs and Payback. After you’ve reviewed this expanded table, let’s move on to what is depicted in more detail.


Level 1: Crowd Control

  • Throughput – Waist-high turnstiles can process up to 30 people per minute, including access control processing time. If you have a lot of two-way traffic during shift changes or lunch, then the max throughput per direction falls to 12 to 15, not 30. Adding more turnstiles to accommodate this traffic pattern affects capital cost.
  • User Education – Waist-high turnstiles do not typically require user orientation training.
  • Metrics Capability – Waist-high turnstiles can count the number of people entering or exiting. The access control system can track all presented credentials. Due to lack of detection sensors or alarms on turnstiles, there is no way to track jumping or crawling infractions.
  • Strategy Implications – With the limited metrics available, you must rely on manned security to verify who is coming and going, process visitors, create infraction reports, etc. You must also manage guard staff’s ongoing training, shift coverage and procedures. You can only track or measure what is reported or observed by the staff. This strategy is vulnerable to distractions, favoritism and absenteeism, which all create opportunities for infiltration. 
  • Payback/ROI – Level 1 payback is its value as a visual deterrent. Due to reliance on security staff to provide all metrics and response, annual, ongoing capital costs are high relative to other Capability Levels.

Level 2: Deterrent

Full-height turnstiles at the perimeter or fence line are used to deter infiltration into a facility or campus.

  • Throughput – Full-height turnstiles handle up to 18 people per minute, including access control processing time. They are most efficient during one-way rush periods. If you have a lot of two-way traffic during shift changes or lunch, then max throughput per direction is seven to nine, not 18. This means you might need to install more turnstiles than planned, which affects capital cost.
  • User Education – Full-height turnstiles typically do not require special user education.
  • Metrics Capability – Full-height turnstiles can count the number of inbound and/or outbound people. Combined with an access control system, you can track submitted credentials. There are no sensors or alarms to track climb over and piggybacking – when two people squeeze together into the same compartment on a single authorization.
  • Strategy Implications – With limited metrics and no piggybacking alarm, unmanned full-height turnstiles are often part of a multi-tiered plan, where other types of security entrances are relied upon to enter and move deeper inside buildings. Therefore, the impact of the overall strategy depends on the Capability Level deployed for the buildings themselves.  
  • Payback/ROI – The payback of full height turnstiles is solely as a perimeter deterrent. Ongoing capital costs are very low (maintenance and tune ups) relative to other Capability Levels because there is typically no direct guard supervision, or they are remotely monitored.

Level 3: Detection

  • Throughput – With access control integration, optical turnstiles with barriers can process up to 30 people per minute, including access control processing time. If traffic becomes heavy in both directions, expect throughput in a single direction in the teens, and plan the number of turnstiles you need accordingly (affecting capital costs).
  • User Education – Because of the sensors, alarms and moving barriers, all users should be trained on safe use.
  • Metrics Capability – Optical turnstiles are equipped with presence detection sensors, and therefore can provide metrics: number of authorized personnel inbound and outbound, and number of tailgating incidents/alarms. Certain models with dense sensor arrays can be set up to alarm and count jumping or crawling attempts. Access control can track all credentials submitted.
  • Strategy Implications – The metrics are similar to waist high turnstiles with an added bonus: you can count tailgating incidents and strive towards elimination. However, you must rely on manned security at the site to respond quickly to alarms, which brings to bear similar ongoing management and costs as with waist high turnstiles.
  • Payback/ROI – The payback of optical turnstiles is in their value as a strong visual deterrent. Due to reliance on security staff to monitor and respond quickly to infractions, annual, ongoing capital costs are high relative to other Capability Levels.

Level 4: Prevention

Level 4 includes security revolving doors and mantrap portals, which are able to detect and prevent tailgating.

  • Throughput –A security revolving door can handle a maximum of 20 people per direction simultaneously, for a total of 40 people per minute. A mantrap portal can process up to six people per minute, but only one at a time. If you require dual authentication, this number will be lower. Capital costs are impacted by how many entrances you need during peak one way and two-way traffic flow periods.
  • User Education – Because of the sensors, alarms and moving parts, a user orientation program is a must.  
  • Metrics Capability – Due to sophisticated near-infrared sensors and optic technologies, Level 4 entrances offer a rich assortment of metrics, such as authorization received, passage completed, tailgating/piggybacking rejections inbound or outbound, biometric access control rejections, safety rejections, and emergency button rejections. You can use the access control system to count rejections and then investigate the optic records to discover why those rejections occurred. Most importantly, through sensor calibration, you can begin to predict and quantify, with a low margin of error, your actual risk of infiltration.
  • Strategy Implications – Detailed and predictive metrics without the need for security staff makes Level 4 the most reliable strategy to prevent tailgating and piggybacking. By understanding and determining false acceptance and rejection ratios, and verifying a door’s performance over time, you can develop an objective, predictable and quantifiable risk that can be managed.
  • Payback/ROI – Level 4 enables the elimination or reallocation of security staff, thus providing a financial payback on the investment. Ongoing capital costs involve routine maintenance only. The financial benefits and strategy implications are the main reasons more and more companies are finding Level 4 appealing.

We’ve only skimmed the surface by showing these Capability Levels and their unique impacts. We hope these articles will motivate a discussion in your organization as to your current vulnerability to tailgating; the possible costs of the wrong person getting into your building; and what commitment of time and resources your organization is willing to make to further limit your tailgating vulnerability.