Horizontal Curve Design

Computes minimum radius R_min, required superelevation e, and spiral length L_s for circular horizontal curves based on speed, friction and rate of change of centrifugal acceleration.

Inputs

Current units: SI – V in km/h, distances in metres.

Design speed Vkm/h

Existing radius Rm (optional)

Provided spiral length Lsm (optional)

Max superelevation e_maxdecimal (e.g. 0.07)

Design side friction fdecimal (e.g. 0.15)

Rate of change of centrifugal accel. Cm/s³ (0.6–0.8 for highways)

Max comfortable lateral accel.for info only

Results

Enter design speed, friction and superelevation limits (and optional R, Ls) then click Compute.

Basic relationships: centripetal demand V²/(gR) is balanced by e + f. Here, R_min = V² / [ g (e_max + f) ]. Transition length L_s is based on L = V³ / (C · R) with V in m/s (internal).