Summary A number of studies have shown that police officers who wear bulletproof vests (BPVs) are significantly less likely to die in the line of duty than officers who do not don vests. Nevertheless, some patrol officers are reluctant to wear them, saying that they are uncomfortably hot and reduce mobility; they represent 8% of all police officers and 47% of all motorcycle officers. Yet refusing to wear a BPV increases their risk of being killed or wounded. Officers in motorcycle units would therefore appear to be among those most exposed to danger, especially because they have to work outside, are close to a heat source (motor), have to wear additional uniform items (jacket, boots, helmet), and the postures and manoeuvres involved in riding a motorcycle require a large range of motion. This research project stems from an earlier ergonomic assessment that underscored the thermal and operational constraints associated with wearing a BPV and from the interest expressed by the OHS community in evaluating the constraints on motorcycle unit officers wearing this type of vest, after the assessment results were made available to members of the Association paritaire pour la santé et la sécurité du travail—secteur affaires municipales (APSAM) and the Association paritaire pour la santé et la sécurité du travail—secteur administration provinciale (APSSAP). The objectives of this exploratory study were therefore to examine the ergonomic constraints associated with motorcycle police officers wearing BPVs, including restricted movement and thermal strain, and then to develop selection and design criteria for vests better suited to the officers’ work. The study method involved both an ergonomic analysis conducted in the field with motorcycle police officers in real situations and an experimental protocol that incorporated “controlled” simulations of work activities. Two police forces took part in the study: a provincial police force and a municipal force. There were five main stages to the method: (1) a review of the literature, including an analysis of the BPV models used and of police force data; (2) an analysis of motorcycle police officers’ activity (n = 5 officers) conducted by means of observations, interviews and a survey specifically about mobility constraints; (3) an analysis of the mobility constraints on officers (n = 16) who wore a vest, conducted by means of experimental simulation; (4) an analysis of thermal constraints when wearing a BPV performed using two parallel approaches, that is: (i) an ergonomic approach to thermal strain during actual work by monitoring physiological indicators such as core body temperature [CBT], skin temperature [Tskin], heart rate [HR] and relative cardiac cost [RCC], and (ii) an experimental approach in a simulation situation to assess the influence of certain determinants on thermal strain, especially the vest, activity and clothing (field, n = 22 bike officers; simulations, n = 16 bike officers); (5) development and validation of BPV selection and design criteria adapted to the characteristics of motorcycle police officers’ work. The results show that motorcycle units play an important role on police forces. The various conditions under which they perform their work, especially the physical, cognitive and environmental aspects, make it demanding, indeed more demanding than working out of a patrol car. The RCC values recorded in the field indicate, overall, moderate work intensity on a physical level, but the motorcycle officers were subjected, several times, to physical demands that were heavy (RCC > 30%), very heavy (RCC > 40%) or even intense (RCC > 50%). Wearing a BPV exacerbates the mobility constraints and thermal strain already omnipresent in their work. The study results for three different models of BPV showed that wearing one reduced mobility and created noticeable pressure points at the “shoulders, crook of the shoulder and underarms,” and greater discomfort on the “sides” and on the “abdomen.” The cut, weight, fit and flexibility of the BPVs studied were not compatible with the major mobility demands of the upper body and arms required to perform the work, or with motorcycle riding, which involves repeated bending and turning of the upper body, movements specific to getting on and off the motorcycle, targeting vehicles with speed detection equipment, directing traffic, etc. Also, the front, sides and pockets of the vests interfered with the equipment in the officers’ duty belts. Most motorcycle police officers were subjected to significant thermal strain, including CBTs of over 38°C, exceeding critical values set by the National Institute for Occupational Safety and Health (NIOSH), the World Health Organization (WHO) and the British Occupational Hygiene Society (BOHS), for repeated and extended periods. All the data converge and provide evidence of these strains: physiological indicators, debriefing comments, survey responses and observations. Like CBT, the mean Tskin was also higher when BPVs were worn. Mean Tskin greater than 35°C were measured for most motorcycle officers (n = 15/18). However, the intensity of the officers’ physical activity turned out to be a determining factor in raising their CBTs, mean Tskin and RCCs, more than the wearing of the vest itself, although the vest does have an isothermal effect that maintains a high body temperature. Thermal strain was present at ambient temperatures of as low as 14°C, or even 9°C when a leather jacket was worn. However, the RCC and EPCT (resting HR increases due to thermal strain) data tend to show that the overall situation does not involve any health risks. The debriefing comments and symptoms noted would be classified in the “moderate heat-related discomfort” category. As for the motorcycle officers’ overall perception, it corroborated the recorded thermal strain data. The many effects of working in heat include fatigue, headache, dizziness, skin irritation, lower vigilance and trouble concentrating. The study findings also show that equipment such as the motorcycle, police belt and other items of clothing, as well as the way they interact with the BPV, constitute other determinants that can exacerbate the thermal and mobility constraints. Wearing other items of clothing on top of one another (undergarments, T-shirt, shirt, pants, socks, boots, BPV, high-visibility safety vest) increases the number of layers of fabric, and therefore the constraints. Suggestions for improvement should focus on the main determinants of the vest’s thermal and mobility constraints, especially (i) the criteria for the covering, choice of textiles (shell and ballistic panels) and manufacture of the BPV; (ii) the fitting method, which must take into account the movements an officer actually makes at work; (iii) alternative cooling technologies for vests; (iv) other items of police equipment; and (v) work organization. Future research should concentrate on, among other things, designing a new light BPV that emphasizes greater flexibility and ventilation, and the development of a logic for the design and purchasing of uniform items that avoids having to wear several layers of fabric or material one top of another.