The effective phase velocity corresponding to the wavelength of 40 m (Ve40) is proposed here as a proxy to provide National Earthquake Hazard Reduction Program (NEHRP) soil classification. This represents an extension of previously proposed approaches that might be of interest for scientists or practitioners who are using methods for estimating the phase velocity that are not allowing an unequivocal separation of modes. With respect to previous works, more extensive numerical simulations were carried out by considering 13,000 VS profiles, both including normally and inversely dispersive configurations. These indicate that Ve40 provides reliable classifications in more than 80% of cases. This percentage of successes is comparable with that of standard measurements (down-hole) when realistic experimental uncertainties are accounted for.