These major trade routes list approximate travel times for wagons to reach their final destinations from stated points, allowing for major stops along the way. For water routes, times are given for travel coming and going to certain spots, allowing for the ocean and river currents. Foot movement along roads and trails (assuming an average load) moves at 1.25 times slower than the listed overland travel time (multiply time by 1.25), while horse travel reduces time by 60% (multiply the time by 0.4).
For example, your party is traveling on foot from Luskan to Mirabar. A caravan takes seven days to travel that distance. A PC band can walk this distance in eight and a three quarters days, arriving at Mirabar on the ninth day out of Luskan (7 × 1.25 = 8.75). To travel the same route on horseback would only take three days (7 × 0.40 = 2.8 days).