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Pathfinder Technical Reference
Path Following in SFPE Mode
being travelled on, speed modifiers and constants associated with the terrain, and
occupant density in the current room.
Base Speed, vb
The occupant’s base speed, 𝑣𝑏 , is defined as a function of density, terrain, and a speed
fraction curve based on the SFPE fundamental diagram. It does not take terrain speed
modifiers or constants into account.
𝑣𝑏 = 𝑣𝑚𝑎𝑥 ∗ 𝑣𝑓 (𝐷) ∗ 𝑣𝑓𝑡
𝑣𝑚𝑎𝑥 is the occupant’s maximum speed as entered in the user interface as Speed.
𝑣𝑓 (𝐷) is a speed fraction as a function of density as follows:
𝑣𝑓 (𝐷) = {
𝑚𝑎𝑥 [𝑣𝑓𝑚𝑖𝑛 ,
1,
𝐷 < .55 𝑝𝑒𝑟𝑠/𝑚2
1
(1 − .266𝐷)] ,
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𝐷 ≥ .55 𝑝𝑒𝑟𝑠/𝑚2
𝑣𝑓𝑚𝑖𝑛 is a minimum speed fraction as defined in the user interface (default=.15), and 𝐷
is the occupant density in the current room.
𝑣𝑓𝑡 is a speed fraction that depends on the type of terrain being traversed by the
occupant. It is defined as
𝑘
1.4
For level terrain (rooms) and ramps, k = 1.40 m/s. For stairs, 𝑘 depends on the step
slope of the stairway. The SFPE handbook defines 𝑘 only for a limited set of known step
slopes as follows:
𝑣𝑓𝑡 =
Stair Riser (inches) Stair Tread (inches) k
7.5
10.0
1.00
7.0
11.0
1.08
6.5
12.0
1.16
6.5
13.0
1.23
Pathfinder uses this information to determine k values for any stairs by constructing a
piece-wise linear function that maps step slope to k values using these known data
points. The step slope of a stair is defined as:
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