A Travis Field
exists at any station that has been moved to or from within the previous three moves, or five moves in the case of Circle Line stations. The strength of the Travis Field is measured in Onds
and is calculated by multiplying the arriving or departing player's line velocity
by the square-root of their Beck's Coefficient
all divided by the relative move number (1, 2 or 3 (and 4 or 5 for Circle Line stations)).
Travis fields are also created by cascades and the value is dispersed among all qualifying stations, from the cascade inception station in each direction along the network with a 0.1 Ond reduction for each interchange.