It is not known exactly when the first motor truck was imported into New Zealand, but its usefulness had been well established by 1912 when it was suggested in Parliament that motor-buses and motor wagons should be used instead of light railways. It was said that much wool was being carried by motor lorry. Another innovation was the service car, which was used in public passenger work in Otago from 1910 onwards. Horses, however, were still used for freighting until after the First World War, mainly because trucks were costly to buy and run. A horse could be shod cheaply and quickly; a set of truck tyres cost £150 or more and often took two days to fit. The war advanced the efficiency and production of motor vehicles and large numbers were available from 1919 onwards, and many returned soldiers were experienced in driving and servicing them.

The following table shows the 10-yearly numbers of trucks, omnibuses, and service cars on the register from 31 December 1925 to 1955, also for 1962 to 1964 (1925 figures for trucks only are available).

*Excludes Government-owned trucks and local body “exempted” trucks, but in the 1964 figures Government-owned trucks are included and local body “exempted” trucks are still excluded.

The growth of the national fleet of commercial vehicles is a significant event of New Zealand's economic history. The railways were the first to feel the effects, and much of the more costly freight traffic was diverted to motor vehicles. The effect is somewhat obscured. Between 1920 and 1930 the tonnage of railway freight traffic rose from 6 million tons to 7,800,000 tons, but it is clear that, but for the competition from road transport, the tonnage carried in 1930 would have been much higher. In the same period fewer passengers were carried in other than the suburban areas. But the motor vehicle made its greatest contribution in the country areas beyond railheads and in urban delivery. It appeared in large numbers during a time when New Zealand was extending its farming frontier. This called for fast, efficient, and economical transport beyond the power of the horse to fulfil, and though horses and railways played a small part, the motor truck filled the need. Road improvements and the invention of pneumatic tyres have increased speeds, loads, and area of operation and have enabled the motor vehicle to exceed even the railways in developmental capacity per unit of capital. But the benefits have not been limited to one industry. The motor vehicle has been a factor of very great importance in the production, for example, of meat and wool and, recently, has shown that it has decisive advantages over its rivals for moving sheep, pigs, and cattle, even over long distances. It has become more and more used in the timber industry and also, though on a more limited scale, in mining.

By 1931 the advantages of motor transport had proved so decisive that the Government decided to limit the activities of road transport to preserve the financial structure of the railways; thus the principle of licensing of road, passenger, and freight-transport services was introduced in the Transport Licensing Act of 1931. It was extended to town carriers, taxicab, and rental vehicle services in 1939, and, in 1949, to harbour-ferry services. This legislation created a partial monopoly in public road transport by limiting entry to the industry. Restrictions on space preclude any analysis of the legislation or of the necessary later amendments, but there is little doubt that the original aim of the legislation to confer on the railways some measure of protection from road transport has been fulfilled. At the same time, the public road-transport industry has expanded considerably, but it is difficult to say just how far its growth has been retarded or its financial results benefited by the licensing legislation.

The efficiency of commercial motor vehicles, such as trucks, as well as omnibuses and service coaches, has advanced considerably in the years following the Second World War. The ratio of horsepower to weight has increased, not only because of improvements in the efficiency of petrol and diesel engines, but also because of the extensive use of alloy metals and plastics in motor bodies. Improved braking systems and transmission, and innovations such as air suspension, have borne fruit in the form of greater safety and comfort for passengers. The use of vehicles specially built to carry certain classes of goods only has been extended. In the dairy industry, which owes so much to the use of the earliest classes of motor vehicles, the modern milk tanker, for example, has brought about considerable economies in the collection and unloading of milk and cream. Much greater use is now made of diesel-engined trucks and passenger-service vehicles from which, in certain classes of work, marked economies can be expected.