The advent of toll roads, regular stage coach services and increased road traffic meant that the old city gates that had been designed for the access of horse and cart now restricted the flow of traffic. Five of them were removed during the 18th century, and all but two of the remainder were demolished the following century. With industrial growth there was a corresponding rapid increase in population for which housing was needed. As all the existing streets were already built up, new houses were built on the remaining open spaces as well as on gardens and land at the rear of existing properties, and others were built outside the area of the old city. Over a period of 30 years, the number of houses in Coventry almost doubled from 2,930 in 1801, to 5,865 in 1831.