NIST Technical Note 1741 

Enhancing Performance and Safety 

in Ambulances through Improved 

Design Standards 

Deogratias Kibira 

Y. Tina Lee 

Mehdi Dadfarnia 

http://dx.doi.org/10.6028/NIST.TN.1741 
 

 

NIST Technical Note 1741 

Enhancing Performance and Safety 

in Ambulances through Improved 

Design Standards 

Deogratias Kibira 

Y. Tina Lee 

Mehdi Dadfarnia 

Systems Integration Division 

Engineering Laboratory 

National Institute of Standards and Technology 

Gaithersburg, MD 20899 

http://dx.doi.org/10.6028/NIST.TN.1741 

May 2012 

U.S. Department of Commerce 

John E. Bryson, Secretary 

National Institute of Standards and Technology 

Patrick D. Gallagher, Under Secretary of Commerce for Standards and Technology and Director 
 

 

 

 

Certain commercial entities, equipment, or materials may be identified in this

 document in order to describe an experimental procedure or concept adequately. 

Such identification is not intended to imply recommendation or endorsement by the 

National Institute of Standards and Technology, nor is it intended to imply that the 

entities, materials, or equipment are necessarily the best available for the purpose. 

National Institute of Standards and Technology Technical Note 1741 

Natl. Inst. Stand. Technol. Tech. Note 1741, 8 pages (May 2012) 

http://dx.doi.org/10.6028/NIST.TN.1741 

CODEN: NTNOEF 
 

 

 

 

 

 

 

Enhancing Performance and Safety in Ambulances through Improved Design 

Standards 

Deogratias Kibira, Y. Tina Lee, and Mehdi Dadfarnia 

Systems Integration Division
 

Engineering Laboratory 

National Institute of Standards and Technology 

100 Bureau Drive 

Gaithersburg, MD 20899, U.S.A 

deogratias.kibira@nist.gov; leet@nist.gov; mehdi.dadfarnia@nist.gov
 

Keywords: Ambulance patient compartment design, 

emergency clinical tasks, modeling and simulation, 

ergonomics, safety. 

Abstract 

This paper describes how modeling and simulation can 

play a major role in developing standards recommendations 

for patient compartment layout of automotive ambulances in 

the United States to improve performance and safety. 

Acquiring necessary information from relevant stakeholders 

is shown as a method that can be used to determine user 

design requirements. The requirements will in turn be used 

to develop design concepts taking into consideration human 

interface with the ambulance work environment. The 

modeling and simulation of clinical care activities in the 

ambulance can be used to evaluate the design concepts and 

determine those that would better meet safety and 

performance requirements. 

1. INTRODUCTION 

About 50,000 ambulances travel on U.S. roads every 

day. In 2010, there were more than 250 U.S. ambulance 

crashes that were reported in the news media. It is likely that 

there are other accidents that did not make it into the news 

[Ballam 2011]. During such accidents, emergency medical 

technicians (EMTs), who ride in the ambulance patient 

compartments while caring for patients, are at high risk of 

suffering injuries. Restraint systems are the first line of 

defense against injuries or death; however, using restraints 

makes it difficult to access items and treat the patients. An 

ideal layout of the patient compartment and location of the 

equipment, medicine, and supplies should optimize 

performance of the EMTs while ensuring their safety. 

It is estimated that ambulance crashes in the United 

States result in one fatality every 10 days and many serious 

injuries. The cost estimates are more than $500 million 

every year [Burns 2010]. The majority of fatalities are 

unrestrained EMTs riding in the patient compartment. 

EMTs have indicated that they would use restraints if it 

would allow some mobility while in transit [Proudfoot et al. 

2007]. The need for mobility depends on such factors as 

necessary clinical care activities; location of equipment, 

medicines, and other emergency medical care items; type of 

seats; and, overall patient compartment layout. Balancing 

the need for safety with the need for mobility will be vital in 

future ambulance compartment design. A uniform 

performance standard for ambulance patient compartment 

design and construction is required to balance the needs of 

safety and performance. 

The General Services Administration’s KKK-A-1822F 

standard is an ambulance procurement specification; it is not 

intended to be used for design requirements [GSA 2007]. 

This and other current design guidance documents do not 

fully address safety alternatives from the perspectives of 

crashworthiness, performance, and ergonomics. The 

National Fire Protection Administration’s NFPA 1917 

standard, on the other hand, specifies the minimum 

performance parameters, essential criteria, and other 

requirements for new automotive emergency medical 

services (EMS) including ambulances. However, it does not 

address much specific to the patient compartment [NFPA 

2010]. 

Because of this, ambulance manufacturers, EMS 

responders, and researchers are teaming together to design 

new patient compartments that balance the safety and 

mobility needs of EMTs. To perform the necessary 

requirements analysis, a number of qualitative and 

quantitative methods are being used. One qualitative method 

is soliciting information from practitioners, ambulance 

manufacturers, and government agencies using a survey. 

Another is to hold a workshop to verify the outcomes from 

the survey and gather more information. 

The rest of the paper is organized as follows. Section 2 

reviews patient compartment layout designs. Section 3 

describes the gap analysis and identifies the needs 

requirements. Section 4 describes the approach to modeling 

and simulation of EMT activities. Section 5 concludes the 

paper. 
 

 

   

 

2. PROBLEM STATEMENTS 

2.1. Background 

The interior of the ambulance patient compartment can 

be laid out in various ways. The traditional layout locates a 

gurney at or near the center with the head of the patient 

facing inwards; a bench seat that can sit three people on the 

curb side; a rear facing attendant’s seat, often called the 

captain’s chair (or airway seat) located at the head end of 

the gurney; and, a CPR seat on the street side of the 

compartment. The CPR seat is located in an area where 

storage cabinets take up space from the ceiling to the level 

of the seated individual’s neck. In the event of an accident 

the head would be stopped but the lower body would 

continue being propelled forward. Such a scenario would 

lead to serious and potentially fatal neck injuries. Therefore, 

the CPR seat is rarely used. The cabinets attached to the 

walls store medicines and other emergency medical care 

items. Most controls, e.g., for HVAC and interior lighting, 

are located at the front and EMTs have to get up to reach 

them. Figure 1 shows the traditional ambulance layout. 

Figure 1. Traditional ambulance layout 

2.2. Problem areas 

2.2.1. Ambulance clinical care 

Since EMTs work in a moving ambulance and perform 

physically demanding tasks, they need a work environment 

that is safe, with occupational hazards minimized or 

eliminated [Gilad and Bryan 2007]. Because the patient 

compartment is a confined workspace, a number of concerns 

arise. The concerns are, mainly: 

 Patient compartment layout and workflow 

 Accessibility of emergency care equipment and 

supplies 

 Equipment mounting 

 Seat type and orientation 

 Applicability of restraint systems 

 Internal and external communication mechanisms 

Other concerns include height of the ceiling above the 

floor, location of the sharps boxes, and height of the gurney 

relative to the seat (See Figure 5). In case of mass casualties, 

an ambulance can be configured to carry additional, noncritical patients. 

2.2.2. Restraint systems 

Seat belts provided to EMTs should offer protection 

from being thrown around in the compartment but allow 

access to patients, equipment, and supplies. However, most 

existing restraint systems rarely do both [Green et al. 2005]. 

Restraint types currently available include lap belts, lap and 

shoulder belts, and tethered seat belts. Lap and shoulder 

belts require sitting with the back against the seat back; such 

a sitting position makes it impossible to sit at the front edge 

to access the patient. The tethered seat belts or mobile 

restraint systems can allow movement from a seated 

position and offer some protection – although the wearer 

would still be swung inside the compartment if an accident 

should occur. EMT seat orientation and cultural practice 

regarding use of seat belts affect the relationship between 

restraint systems and actual safety. 

2.2.3. Performance 

EMTs must have appropriate equipment and supplies to 

optimize pre-hospital care. The American College of 

Surgeons (ACS) Committee on Trauma (COT), American 

College of Emergency Physicians (ACEP), and the National 

Association of EMS Physicians (NAEMSP) have 

collaborated to produce a standard list of equipment for both 

the United States and Canada. For basic level services that 

list includes equipment for ventilation, monitoring and 

defibrillation, immobilization, communication, and 

obstetrics. There is also a need for bandages, towels, 

infection control, injury prevention, and other miscellaneous 

equipment. For advanced level services, the list includes all 

basic level supplies plus vascular access, cardiac, 

medications, and other advanced equipment. The full list 

can be found at [ACS 2009]. In current U. S. ambulance 

designs, most of the equipment is carried in interior storage 

cabinets although some of the equipment can be carried in 

external cabinets. 

3. REQUIREMENTS ANALYSIS 

3.1. Gap Analysis 

This section describes the requirements gap analysis 

that was performed using SysML [Object Management 

Group 2008]. SysML is a general-purpose graphical 

modeling language that supports the analysis, specification, 

design, verification, and validation of complex systems 

[Friedenthal et al. 2009]. We examined and compared the 

NFPA 1917 standard with three other standards: Alberta 

Ambulance Vehicle Standards Code, Australian/New 

Zealand Standard 4535, and British Standards Institution BS 

EN 1789. The Alberta Ambulance Vehicle Standards Code 

applies to the general construction of ambulances in Canada 

[Government of Alberta 2010]. The Australian/New 

Zealand Standard 4535 applies to restraint systems for 

people and equipment in motor vehicles specifically 
 

 

 

 

 

 

 

 

 

designed as, or modified and converted into, ambulances for 

transportation of occupants and equipment [AS/NZS 1999]. 

The British Standards Institution BS EN 1789 specifies 

requirements for the design, testing, performance, and 

equipping of road ambulances used for the transport and 

care of patients. It contains requirements for the patient’s 

compartment [BSI 2007]. 

Four SysML diagrams that outline patient 

compartments’ requirements have been created for each of 

the standards mentioned above. The requirements gaps can 

then be identified by comparing these diagrams. We used a 

matrix table that (1) depicts different sets of requirements 

for the patient compartment and (2) identifies relationships 

between these requirements to show the comparison of two 

standards. For example, Figures 2 and 3 are obtained by 

comparing two standards; the Alberta Ambulance Vehicle 

Standards Code and the Australian/New Zealand Standard 

4535, with NFPA 1917. In each table, the row represents the 

requirements for the patient compartment in the standard 

that we desire to compare to the NFPA 1917. The column 

represents corresponding NFPA requirements that may 

already fulfill a requirement set by the standard. An arrow 

sign, ‘↑’, is inserted in the table if the NFPA 1917 

requirement corresponds to the standard’s requirement item. 

Rows that have not been filled with the arrow sign 

essentially exemplify a requirement in the standard that does 

not have a corresponding equivalent in the NFPA 1917. 

Note this does not necessarily mean that the NFPA 1917 is 

lacking, since it is possible the other standard’s requirement 

does not comply with the American emergency medical 

services system. In essence, this analysis enables us to 

identify the areas where one standard might have some 

strength or advantage over another. All columns are filled 

indicating that both standards have an equivalent 

requirement for all sampled specifications in NFPA 1917. 

However, some rows are not filled indicating an inadequacy 

on part of the NFPA 1917. For example, the Australia/New 

Zealand standard 4535 specifies wheelchair accommodation 

and labeling at each internal compartment currently lacking 

in the NFPA 1917. 

3.2. Design Needs 

Through requirements gap analysis as well as ridealong trips, domain-experts interviews, and industry survey, 

we identified a set of design needs: 

3.2.1. Seating 

The ambulance seat should allow EMT to: 

	 easy access to the patient 

	 easy access to the monitor and controls 

 easy access to equipment, supplies, and medicines 

 face and eye contact with patient 

 ride and perform task safely and ergonomically 

The ambulance seats should also satisfy the needs of EMTs 

from diverse population. 

3.2.2. Working Environment 

The ambulance working environment should provide 

the capability to: 

 transport and care for more than one patient safely 

and ergonomically 

 allow appropriate lighting, temperature, ventilation, 

and noise level inside the patient compartment 

	 allow appropriate communication mechanism for 

the EMT to communicate with the ambulance 

driver, hospital, etc. 

	 supply the required power and power outlets to be 

used by the communication system, equipment, etc. 

	 place monitors, controls, equipments, supplies, 

cot, disposal containers, etc. at appropriate, secure 

locations for EMT to access easily, effectively, 

safely, and ergonomically 

 appropriate height and room for EMT to move 

around 

 ingress and egress the patient compartment safely 

3.2.3. Restraint Systems 

The ambulance restraint systems should allow EMT to: 

 buckle and unbuckle easily and quickly 

 access the patient from a restrained position safely 

and ergonomically 

	 access monitors, controls, equipments, supplies, 

medicines, etc., from a restrained position safely 

and ergonomically 

	 perform patient care safely and ergonomically 

The restraint systems should also satisfy the needs of 

 EMTs from diverse population 

 patients from diverse populations 

Each of above design needs is continuing to be 

examined for the development of design requirements. A 

preliminary set of design requirements is currently being 

developed. We are also working with the ambulance 

community to review the completeness and accuracy of the 

ambulance design needs. 
Figure 2. Requirements traceability matrix for NFPA 1917 (column) vs. Alberta Ambulance Vehicle Standards Code (row) 
 

 

 

 

Figure 3. Requirements traceability matrix for NFPA 1917 (column) vs. Australian/New Zealand Standard 4535 (row) 

4.	 DESIGN CONCEPT EVALUATION USING 

SIMULATION MODELING 

4.1. Design concepts 

The analysis of user needs and requirements described 

in the previous sections will be used to develop design 

options that satisfy those needs. The development of interior 

layout design concepts is complex as it is constrained by 

factors such as space limitations and clinical equipment 

designs. However, it is not practical or feasible to have a 

design that fulfills all requirements, which would be an ideal 

design layout. Therefore, alternative optional design 

concepts, based on given criteria can be developed that 

satisfy as many of the requirements as possible. For 

example, a satisfactory design should locate and affix the 

monitor, pulse oximeter, and essential drugs closest to the 

EMT and permit oxygen and IV administration from a 

seated position. This design may necessitate repositioning of 

cabinets and redesign of the EMT seat for it to be movable 

and changeable in orientation. Design concepts to satisfy 

this requirement may deviate from the traditional layout. 

4.2. The benefits of modeling 

The design options will be systematically evaluated 

using virtual-reality simulation models of EMTs performing 

a range of emergency care activities. This type of simulation 

has several benefits over traditional physical mockups. First, 

decision makers can evaluate new designs, layouts, 

configurations, and systems before committing resources to 

their acquisition or implementation; thereby reducing the 

risk of making poor decisions. Second, they can mimic, with 

high fidelity, the human interactions with the environment, 

the patient, and the equipment. Third, since they allow 

humans to enter and interact with a model of the ambulance 

interior, these simulations can also be used in the training of 

personnel. Fourth, different equipment and supplies 

placements, tasks, restraint systems, and human 

performances can be evaluated very quickly at minimal cost. 

This means that human factors and physical layouts can be 

modeled and evaluated simultaneously. Figure 4 shows the 

design concept evaluation process. 
 

Figure 4. Modeling and layout design evaluation process 

4.3. Task analysis 

Task analysis is the breakdown of work elements, 

determination of precedence relationships, and 

establishment of how the work elements are to be 

performed. Major tasks performed by EMTs include 

preparing the ambulance, driving to the patient site, treating 

the patient at the site, driving the patient to hospital, 

providing additional care in transit, and delivering the 

patient to the hospital. Each of these tasks can be broken 

into work elements. Each such element has a description of 

constraints and procedures. For example, one of the work 

elements in the treat-patient task is to determine the blood 

circulation level. The procedure would be to check the heart 

rate and/or blood pressure. The constraint would be the type 

and location of the stethoscope or blood pressure monitor in 

the ambulance. The challenge is to identify EMT tasks and 

work elements that will form the basis for evaluating 

different layout designs for the patient compartment 

including the placement of medicines, tools, and equipment. 

4.4. Evaluating different designs 

To evaluate different layout designs we need to build 

and integrate models of the EMT, the patient, and the 

patient compartment. The conceptual design of the 

compartment interiors and accessories would be modeled 

using a 3D graphics modeling tool. Simulating the EMT 

activities and patient care requires a human simulation tool 

to accurately depict all movements and tasks. For example, 

the tool must have a feature to allow the mannequin to 

grasp/release objects and to detect/avoid collisions with 

surrounding objects. It must also measure and display 

distances between two points. This is necessary to establish 

the viability of various human postures and flexibility 

required of any proposed restraint systems. To build the 

patient model, we must determine a number of medically 

critical points such as wrist, mouth, and upper arm with a 

patient lying or sitting on the gurney. 

To more accurately duplicate all movements and the 

actions of limbs and digits, the simulated human body 

model should be an articulated figure composed of different 

segments, and be easily manipulated to model different 

postures and positions that an EMT would assume to 

perform various tasks. The design of the patient 

compartment requires a compatible format so that it can be 

imported into the human modeling software tool; either as a 

complete work environment or as separate sections. 

As an example, Figure 5 shows two simulated EMTs in 

a traditional ambulance layout trying to reach a simulated 

patient’s mouth and right arm from seated positions. The 

mannequins are simulating EMTs (one male and the other 

female of average stature) that are restrained with lap belts 

trying to reach and treat a patient. The Figure shows that 

from a bench seat, it is impossible to reach the right wrist of 

the patient without unbuckling. But the mouth is readily 

accessible from the captain’s seat. 

Additionally, Figure 6 shows a configuration for a 

design concept where a pad attached to the bench seat can 

allow a seated EMT to slide forward to access the right hand 

wrist while remaining restrained. The Figure shows that the 

EMT can reach the wrist in this arrangement. This indicates 

that if a bench is designed so that it has segmented cushions 

(life a sofa) placed on a platform that able movement 

backwards and forwards, flexibility can be improved. 

4.5. Experiments and evaluation 

The EMT in the interior of a patient compartment 

works in a moving work environment. Experiments can be 

carried out by varying a number of factors to evaluate safety 

and the EMT’s performance. Some of the factors to vary 

between experiments include: 

 Size, gender, stature of EMTs 

 Type of ambulance 

 Interior dimensions of the ambulance 

 The layout of furniture 

 Location of equipment, supplies, and medicines 

 Clinical care activities 

 Restraint systems. 
 

Figure 5. EMTs trying to reach different parts of a patient. 

Figure 6. The EMT on a bench cushion placed on a platform that can slide forwards. 
 

 

 

 

 

 

 

 

 

5.	 CONCLUSION 

This paper introduces the current inadequacies in 

design and safety of ambulances and discusses the problems 

associated with balancing efficiency and safety of 

emergency medical care in an ambulance. It has shown that 

the existing standards do not facilitate solutions to these 

problems. This paper advocated the use of systems 

engineering modeling (using SysML) to identify gaps in 

those standards and to specify requirements for new solution 

designs. It is also shown that modeling and simulation tools 

could be used to evaluate alternative designs and scenarios 

to obtain decisions on solutions. These solutions will 

involve new layouts for the patient compartments and new 

restraining systems for the EMTs. Robust designs and 

recommendations for future ambulance design standards can 

be obtained using a combination of these approaches. 

ACKNOWLEDGEMENT 

The US Department of Homeland Security Science and 

Technology Directorate (DHS S&T) Human 

Factors/Behavioral Sciences Division sponsored the 

production of this material under Interagency Agreement 

HSHQDC-11-X-00049 with the National Institute of 

Standards and Technology (NIST). 

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