ESDU 91043 presents methods for estimating speed-up factors for mean wind speeds over hills@ embankments@ escarpments and valleys. The methods treat all regions of a hill@ including shelter regions near the foot and account for the local profile. Three-dimensional effects and wind inclination to the ridge line can be taken into account. Interference effects from other nearby topography can be assessed@ and guidance is provided for the effects of flow separation on steep topography. Two methods are given: a simple graphical approach that is accurate for simple embankments but is less accurate for rounded hills because it only accounts for the overall shape@ and a more precise method that accounts for the detailed shape of the hill. Irregularly-shaped hills with bulges and depressions@ and multiple hills@ are treated by the method of superposition@ that is@ each irregularity is treated as a separate isolated hill or valley and the contribution to speed-up added to the other contributions for an overall solution. The methods were derived from data obtained using solutions of the Navier-Stokes equations@ calibrated against both full-scale and wind-tunnel measurements. The methods given here are incorporated in computer program ESDUpac E0108@ see ESDU 01008.