Casual - 5-10 minute walk so maybe 750-1000m?
Walk to daily transport though - that is another story. When considering IP's for this factor of an overall walk-score, I define the 'Goldilocks' zone to be 500-1500m walk to train/bus station (hill factor notwithstanding!).
People might say 'wouldn't lower than 500m be the better Goldilocks zone?'. IMHO I think 500m is enough to negate the noise factor of trains. Tenants in my experience are increasingly becoming noise-adverse, and something 200m to train station can sometimes be harder to mass-rent!
