Curb-sitting: Evidence-based tactic or illusion of safety?

Little empirical evidence guides us on how much time is necessary to create an adequate reactionary gap


Originally published on the Force Science Institute website. Republished here with permission.

By David Blake, Ph.D.

“Do me a favor and have a seat on the curb until we figure this out.”

Undoubtedly, many of you have either given or heard some version of this direction, the belief being that suspects sitting on the curb will have reduced mobility and thereby pose less of a threat than suspects left standing.

Although critics of curb-sitting have argued that the tactic is demeaning and unnecessary, it is defended as a reasonable de-escalation option, one that reduces a suspect’s opportunity to commit assaults.

Proponents of curb-sitting and other subject control tactics might point to the U.S. Supreme Court, which has repeatedly observed that, during detentions or arrests that may give rise to sudden violence, the risk of harm to both the police and the community is minimized if officers exercise unquestioned command of the situation. [1]

For police and community safety, curb-sitting theoretically makes sense. The question is whether curb-sitting provides police with an effective officer-safety tactic, or does it merely create an illusion of safety?

In our recent study, "Curb sitting’: An evidence-based policing practice or an officer safety myth?", Joel Suss, Duane Wolfe, Güler Arsal and I set out to test this theory.

Standing vs. 3 Seated Positions: The Study

In our study, we asked four questions:

1. Are subjects sitting on a curb with their legs extended [2] slower to get up and sprint 5 feet than when sitting with their knees bent and ankles crossed (i.e., yoga “Lotus style”)?

2. Are subjects sitting on a curb with their legs extended and ankles crossed slower to get up and sprint 5 feet than when sitting with their legs extended but with their ankles uncrossed?

3. How fast can a standing subject sprint across distances of 3, 4, 5 and 6 feet?

4. Based on our research, does curb-sitting result in more response time than allowing subjects to stand?

Extended or Bent Legs: Did it Matter?

When subjects began seated with their knees bent and ankles crossed, they were on average .07 s faster to get up and sprint 5 feet than when they sat with their legs extended.

Whether the extended leg subjects crossed their ankles or not made no practical difference in their sprint times. The times reflected in Table 1 show just how close these trials were (M = mean or “average” / SD = standard deviation).

Table 1
Table 1

Sitting or Standing: Who was Faster?

In our study, we also tested how long it took standing participants to cross distances of 3, 4, 5, and 6 feet (See Table 2). Notably, we found that each additional foot of distance resulted in a statistically significant increase in time.

Table 2
Table 2

As readers may have guessed, participants starting from a seated position required more time to cross 5 feet than those starting in a standing position. In all cases, subjects seated with legs extended (both crossed and uncrossed) averaged 1.355 s to cross 5 feet, while those who started from a standing position averaged only 1.096 s.

So, for officers standing 5 ft from a suspect, curb-sitting offers a potential response time advantage of a quarter of a second (.25 s). The question is whether our “statistically relevant” research findings translate to a real-world officer-safety advantage. Let’s discuss why that may not be the case.

Making Sense of an Extra Quarter Second

This study only begins the conversation on curb-sitting tactics, and we recommend the results be evaluated with care. Readers of this study should be clear on our findings.

First, the time benefit between having a person sitting “Lotus style” compared to extending their legs, averaged less than 100 milliseconds (0.07 s). Whatever advantage you might imagine, that is far less time than it takes to blink.

Second, the time to cross 5 feet from a seated/legs extended position is about 250 milliseconds (0.259 s) slower than standing. Again, blink, and you may extinguish any perceived advantage.

Although “statistically significant” findings are important in the research context, it would be inappropriate for readers to walk away believing curb-sitting is sufficient for officer safety. More research is needed to measure curb-sitting variants before they can be compared to what we know about officer response times (e.g., would sitting on a flat surface rather than a curb further impede mobility?).

In the meantime, as we plan for future research, we can use this time to evaluate our study in the context of past related research.

Comparing Research

Force Science students and regular readers likely noted the time differences between our study and other research on sprint times. In "The influence of start position, initial step type, and usage of a focal point on sprinting performance" (“the Sprint Study”), researchers found that participants with a forward focal point sprinted approximately 3 and 7 feet in an average of 0.31 s and 0.59 s respectively. These times are much faster than our findings across similar distances (Table 2).

The slower times in our most recent study are likely based on the different procedures used by the participants.

In our study, participants began at the sound of an audible stimulus, whereas the Sprint Study used a self-initiated start. Using an audible signal meant our times would have included the perception and reaction times of the participants. It may be useful for future research to include self-initiated starts from various curb-sitting positions. This simple modification may allow findings to be further generalized to real-world conditions.

Another difference between studies is that the Sprint Study participants sprinted through the finish line (i.e., consistent with a suspect intent on fleeing). In our study, we had participants strike a pad on a table, which resulted in first slowing or stopping. Our research method was intended to represent the timing of a specific type of assault (i.e., no incentive to sprint past the officer). Consequently, it resulted in a notably slower sprint time than those subjects running through the finish line.

Conclusion

Law enforcement continues to focus on the safety benefits of time, distance, shielding (i.e., cover, barriers, concealment) and de-escalation. However, little empirical evidence guides us on how much time is necessary to create an adequate reactionary gap. At this point, we can only say that curb-sitting provides more time – but not necessarily enough time.

Anecdotal evidence has been the foundation of policing tactics, techniques and training for decades. Certainly, the lives of many officers and community members have been saved by stewarding the most effective and often hard-learned lessons from generation to generation.

Of course, researchers and other academics are eager to support policing with evidence-based tactics, and our communities and civic leaders increasingly demand that we do. I agree with Sandel et al.’s observation:

Little is known about how quickly and effectively an officer can respond to different types of threats; yet this is exactly the type of research that should inform public, court, and police perceptions of use of force events. Better understanding of these factors can help protect the police by helping them to understand and avoid dangerous situations. The public is also protected when police have a clear understanding of the dynamics of these situations and their actual response capabilities, resulting in better decisions about when force should be utilized and when it should not." [3]

As we progress in our research efforts, we expect future research on curb-sitting to involve naturalistic conditions (e.g., stress, self-initiated starts, visual movement cues). We look forward to testing the influence of offline movement by officers (forward, backward, lateral), the associated time to draw and accurately deploy tools (TASER, OC, baton, or handgun), and the time needed to execute empty-hand skills.

Let us know where you would like to see our research go and how we can help you identify and develop evidence-based field tactics for increased officer and community safety. Email suggestions and comments.

References

1. See Brendlin v. California, 127 S. Ct. 2400 (2007) (citing Michigan v. Summers, 452 U. S. 692 (1981).

2. For this question, feet extended could include either ankles crossed, or ankles uncrossed.

3. Sandel WL, Martaindale MH, Blair JP. (2021). A scientific examination of the 21-foot rule. Police Practice and Research. 22(3):1315. 

Bibliography

Blake D, Suss J, Wolfe D, Arsal, G. (2022). ‘Curb-sitting’: an evidence-based policing practice or an officer safety myth? Police Practice and Research.

Blake D, Bartel L. (2018). Holster and handgun: Does equipment affect response time? Law Enforcement Executive Forum, 18(2).

Dysterheft JL, Lewinski WJ, Seefeldt DA, Pettitt R. (2013). The influence of start position, initial step type, and usage of a focal point on sprinting performance. International Journal of Exercise Science, 6(4).


About the author

David Blake, Ph.D., is a retired California peace officer and a court-certified expert on human factors psychology and the use of force. He has significant experience teaching use of force and human factors psychology to law enforcement officers in several states. David has undergraduate and graduate degrees in criminal justice and psychology. He has authored over 30 professional and peer-reviewed journal articles on the application of human factors psychology to first responders and their operational environments. David continues to conduct research on police deadly force and human factors psychology. He is the lead consultant at Blake Consulting and Training.

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