Travel distance

Travel distance is the length of the path an occupant must follow along an escape route to reach a specified exit or place of safety. It is measured along the available walking route rather than as a straight line through the building. Fixed obstructions, corridors, doorways and changes of direction determine that path.

The term describes distance, not the time required for evacuation. Travel time also depends on walking speed, occupant characteristics, smoke, direction and queues at restrictions. Pre-movement activities occur before that travel and must be considered separately.

Travel distance is used in both prescriptive provisions and engineering analysis. Its endpoint and measurement convention must be stated, because different routes or destinations produce different distances. A limit from one jurisdiction cannot be applied to another route without that context.

Definition and measurement

Measurement starts with an occupant location and ends at the destination specified by the escape method. The path must be one that can actually be walked. Measuring diagonally through furniture, partitions or other fixed obstacles would misrepresent that route.

C/VM2, second edition, 2025, uses orthogonal path segments for horizontal travel to the nearest exit. Where fixed obstructions are known, the path is measured around them. This is a measurement convention within New Zealand's verification method.

Travel distance follows the usable path, not a straight line through obstructions. Based on Ministry of Business, Innovation and Employment (2025), p. 32.

An orthogonal path follows the directional geometry of the space rather than a diagonal shortcut. It can represent movement along aisles and around room features. The relevant segments should be traced on the actual layout rather than inferred only from room area.

The nearest exit is not necessarily the exit used by every occupant. Familiarity, signage, crowd flow or smoke can lead people to another route. A design based on nearest-exit distance should be checked against the intended evacuation strategy and plausible route choices.

The measurement should also use the correct destination. A protected doorway, an adjacent safe compartment and the final outside exit are different endpoints. Extending or shortening the path without stating that endpoint changes the meaning of the distance.

Distance within means of escape

Means of escape includes the complete connected route and its physical and operational features. Travel distance describes one geometric property of that system. It does not establish route capacity, fire protection or whether occupants can find the exit.

New Zealand performance criteria reproduced in the 2005 International Fire Engineering Guidelines (IFEG) connect route length with the mobility of users. The same criteria separately address obstruction, size, fire-spread resistance, signage, illumination and safe use. These distinct requirements show why distance is only one part of escape design.

The number of available paths also interacts with distance. An alternative route can offer another way to safety if the nearest path is affected by fire or obstruction. Its usefulness depends on its own length, protection and accessibility rather than its presence on a plan alone.

A Protected escape route can provide a destination partway through the complete journey. Reaching that protection may reduce exposure even if occupants still have further to travel. The distance to protection and the distance to final safety should not be confused.

Travel distance can be affected by later alterations. Moving a partition, creating a new obstruction or changing the use of a room can alter the actual path. The original dimension should not be assumed to remain valid after those changes.

Relationship with travel time

Distance divided by an appropriate speed gives an estimate of unobstructed travel time in simple methods. That estimate applies only to the section represented by the speed and route. It does not include the full behavioural response or every queue along the escape path.

For a route section with constant representative speed, travel time is distance divided by speed.

$$t_{\mathrm{t}\mathrm{r}\mathrm{a}\mathrm{v}}=\frac{L_{\mathrm{t}\mathrm{r}\mathrm{a}\mathrm{v}}}{S}$$

Symbol	Description	Unit
$t_{\mathrm{t}\mathrm{r}\mathrm{a}\mathrm{v}}$	Travel time for the route section	s
$L_{\mathrm{t}\mathrm{r}\mathrm{a}\mathrm{v}}$	Length measured along that section	m
$S$	Representative travel speed along the same path	m/s

The distance and speed must use the same direction of measurement. For example, a stair-slope speed requires distance along the slope, rather than the horizontal projection of the flight. Proulx explicitly makes that distinction in the movement relationships.

For a worked horizontal illustration, take a 40 m route at 1.2 m/s. Both values occur in New Zealand’s C/VM2, second edition, 2025: the speed is its horizontal cap, and 40 m is a specified single-direction limit. The distance limit applies to unfamiliar occupants within the method’s fire-blocks-exit scenario, rather than to every escape route.

$$t_{\mathrm{t}\mathrm{r}\mathrm{a}\mathrm{v}}=\frac{40}{1.2}=33.333\dots \mathrm{s}⟶34\mathrm{s}$$

The result is rounded upwards because it is a required time. It covers walking at the assumed constant speed only. A lower calculated speed, a queue or time spent deciding to leave would increase the total time beyond this simple illustration.

This calculation does not demonstrate compliance merely because its distance equals a published limit. The scenario also addresses whether a viable route remains when fire blocks an exit. Its route arrangements, occupant allocation and other conditions still form part of the verification.

Walking speed varies with occupant characteristics and conditions. Proulx describes differences between unrestricted movement, groups and stair descent. A single generic speed can therefore misstate the time for a particular population or route.

Crowd density affects speed. People can move freely with space between them, but their gait becomes constrained as density rises. The same corridor length can consequently require different times at different occupant densities.

Smoke can reduce speed and cause occupants to change routes. The Australian Building Codes Board (ABCB) reports no reliable general correlation for walking speed in smoke and distinguishes non-irritant from irritant conditions. Clear-air travel calculations do not capture those effects automatically.

C/VM2 uses a maximum horizontal speed of 1.2 m/s in its specified travel-time method when a higher calculated value would otherwise result. This is an input limit within that New Zealand method, not a universal walking speed for all occupants.

Queues and route capacity

Travel along a route differs from passing through a restriction. Proulx distinguishes movement time to a destination from flow time through part of the circulation system. A complete assessment needs both forms of time.

Travel distance alone does not determine movement time. Based on Proulx (2002), pp. 3-347–3-348 and Ministry of Business, Innovation and Employment (2025), pp. 32–33.

Exit capacity can govern how quickly a group leaves even where travel distance is short. If arrival demand exceeds the flow through a doorway or stair, a queue develops. The delay depends on the number of people and the effective flow through that restriction.

C/VM2 compares the time to reach a doorway with the time required for occupants to flow through it. The greater governs evacuation from the space in that method. This procedure identifies two distinct time components rather than treating distance as always dominant.

Downstream restrictions can be more important than the nearest exit. C/VM2 calls for the entire escape route to be checked, because occupants can encounter another limitation closer to the final exit. Measuring only distance to the first door would miss that constraint.

Effective width can be smaller than measured width. Boundary layers near walls, rails and obstacles reduce the stream width used in flow calculations. Travel distance and effective width are therefore separate geometric inputs with different effects on the result.

Exposure along the route

Longer travel can mean longer exposure to a changing fire environment, but the relationship is not purely geometric. Conditions along the route and the timing of fire development determine what occupants encounter. Protection and smoke control can alter those conditions.

C/VM2 includes a method for radiation exposure when occupants pass particular windows or glazed panels. It uses the distance travelled while exposed and a specified speed within defined limitations. The method applies to its New Zealand scenario and is not appropriate for every occupant or arrangement.

Route length must be assessed with exposure and destination protection. Based on Ministry of Business, Innovation and Employment (2025), pp. 34–37.

That exposure calculation uses a specified speed of 1.0 m/s along the part of the path exposed to the defined radiation level. This is a different input from the horizontal travel-speed cap used elsewhere in the method. The window analysis also excludes mobility-impaired occupants and requires more detailed treatment for multiple windows, where exposures accumulate over time.

A route passing through a smoke-affected space may be rejected even if it is shortest. Occupants can choose another path or wait for assistance when conditions become difficult. The effective travel distance then follows the route actually selected rather than the planned shortest line.

Fire in an escape route itself presents a special scenario. C/VM2 asks whether a viable route remains, including multiple routes where required. A nearest-exit calculation alone cannot demonstrate that the path remains available under this scenario.

Distance to a place of safety should be evaluated with the protection offered at the destination. A shorter path to an unsuitable space does not achieve the same objective as a longer path to a protected one. The endpoint must satisfy the intended safety function.

Prescriptive and performance-based use

Prescriptive design can specify maximum distances for defined occupancies and arrangements. Such limits are part of a wider set of provisions, not independent measures of safety. The building type, protection and measurement convention must match the rule being applied.

The IFEG examples show that escape requirements can address travel distance alongside occupant numbers, building height, hazards and installed systems. These relationships are expressed differently across codes. A number from one document cannot be assumed to transfer to another.

Performance-based analysis can evaluate the time associated with a route instead of relying only on a distance limit. It must then include appropriate speeds, queues, response times and environmental conditions. This is a broader analysis, not permission to use any preferred speed.

A regulatory verification method may prescribe the exact inputs to be used. C/VM2's speed, flow and boundary-layer provisions apply within its own second-edition framework. They should not be mixed casually with values from another method without a documented basis.

Extending a distance in a design requires review of the consequences for the complete escape system. Additional protection or management may alter exposure or movement, but their performance must be demonstrated. Distance cannot be assessed as an isolated concession.

Analysis, evidence and uncertainty

The route should be traced on a current building plan and checked against the constructed arrangement. Fixed obstructions and door positions must match the building in use. Discrepancies between design and operation can change both distance and destination.

Occupant groups may require separate paths and speeds. Staff assisting patients, families gathering before departure and visitors unfamiliar with the building can produce different effective routes. A single nearest-exit calculation may not represent those groups.

Observed evacuation data can provide useful comparisons, but their context matters. Proulx describes drill and incident results that vary with building, warning and population. A measured speed from one event should not be used as an exact property of every route.

Models should also distinguish travel from queuing and pre-movement. IFEG warns that simple hydraulic models often assume simultaneous departure and uninterrupted movement. Those assumptions can understate total time even where the measured distance is correct.

Changes in elevation require particular attention to the speed basis. Proulx distinguishes stair-slope movement from horizontal walking and gives empirical values for particular study conditions. Horizontal distance or speed alone cannot describe the complete stair journey.

Van Rossum describes the stair travel line along the fronts of the treads. For a straight flight, its length follows from the horizontal run and vertical rise using the Pythagorean relationship. Landings and subsequent route sections remain additional distances, so a storey height alone does not describe the complete journey.

Smoke analysis should be linked to the timing of arrival along the path. Conditions can change while occupants prepare and travel, so a single static visibility value may not represent the whole route. Irritant smoke can also alter the choice of path rather than only the speed along it.

Common misunderstandings

Travel distance is not a straight-line distance between two points. The path must follow the actual available route around fixed obstructions and through required openings. A plan dimension that ignores those features does not satisfy the cited measurement concept.

It is also not the same as evacuation time. Response, preparation, walking and queueing contribute to total time. Two routes of equal length can produce different evacuation outcomes when their capacities and conditions differ.

The shortest path is not automatically the safest or the one occupants will choose. Fire conditions, protection and familiarity can make another route preferable. Analysis should retain those possibilities rather than assuming universal nearest-exit behaviour.

A distance limit from a code is not a universal physical threshold. It belongs to a jurisdiction, building type and set of related provisions. The applicable edition and its measurement rules must be identified before comparison.

See also

• Protective action decision model
• Affiliative behaviour
• Evacuation lift

References

• Australian Building Codes Board, National Research Council of Canada, International Code Council, & Department of Building and Housing New Zealand. (2005). International fire engineering guidelines (2005 ed.). Australian Building Codes Board.
• Australian Building Codes Board. (2020). Fire safety verification method data sheets (Version 1.1).
• Ministry of Business, Innovation and Employment. (2025). C protection from fire: Verification method C/VM2 (2nd ed.). New Zealand Government.
• Proulx, G. (2002). Movement of people: The evacuation timing. In P. J. DiNenno (Ed.), SFPE handbook of fire protection engineering (3rd ed.). National Fire Protection Association.
• Van Rossum, E. (2027). Introduction to Fire Safety Engineering. Fire Safety Academy.