This article is a travel topic
Since the 1960s overlanding has been a popular means of travel between destinations across Africa, Europe, Asia (particularly India), the Americas and Australia. The "Hippie Trail" of the 60s and 70s saw thousands of young westerners travelling through the Middle East to India and Nepal.
At 9,288km the Trans-Siberian Railway is one of the longest overland journeys in existence today, taking 7 days to reach Vladivostok from Moscow, and providing an alternative to air travel for journeys between Europe and Asia.
The introduction of Japan's high speed railway Tōkaidō Shinkansen in 1964 changed the face of rail travel. The railway has carried more than 4 billion passengers and its new N700 series trains are capable of 300km/hr. France's TGV attains similar speeds, making it faster than air travel for many journeys. It has expanded into other European countries. Korea and the USA now also have some high-speed lines. China is in the process of building what will be the world's largest such network; see High-speed rail in China.
Bus == Truck
The Silk Route or Silk Road historically connects the Mediterranean with Persia and China. Today the route refers to overland journeys between Europe and China, taking either the northern route - through Russia and Kazakhstan - or the southern route - through Turkey, Iran, Pakistan and North India - to Urumqi or Xian in China. These routes are still popular today, with companies such as Oasis Overland [] and Odyssey Overland [] offering tours on the southern route.
One of the most common - and longest - overland expeditions is in Africa, connecting Cairo in Egypt with Cape Town in South Africa. The route covers more than 10,000km and usually takes in Sudan, Kenya, Tanzania, Zimbabwe and Namibia along the way. Overland operators in these areas include Dragoman [],Oasis Overland and African Trails.
The traditional Trans Africa route is from London to Nairobi, Kenya and Cape Town, South Africa. The route started in the 1970’s and becaming popular with small companies using old Bedford four wheel drive trucks carrying about 20 people each Also independent travellers; normally run by or groups of friends in 4x4 Landrovers headed out from London from November to March every year, the winter months been considered the best to cross the Sahara. The usual route was from Morocco to Algeria with a Sahara desert crossing into Niger then Nigeria in West Africa, followed by a month long journey likened to Joseph Conrad Conrad’s “Heart of Darkness” through the forests of Zaire with the trucks surfacing into the relatively modern word in Kenya. From Kenya the last leg was south through Tanzania to either Zimbabwe or South Africa. The writer Shiva Naipaul travelled in an Overland truck and wrote of it in his novel North of South, he was disparaging of the people on the truck and their motives for travelling. The route has changed dramatically with border closures and no go zones with the closure of Zaire now the DR Congo and the Darfur crises' forcing the biggest change in the route. The routs has since the year 2000 reversed itself somewhat with truck now crossing from the north to the south of Africa following near to the west coast all the way from Morocco to Cape Town, the biggest recent change in the route been made possible by the opening of Angola to tourism letting vehicles pass into Namibia into South Africa. Leaving then to complete the old route by turning north in Cape Town to travel to Nairobi and on to Cairo.
The second most popular route was the Nile, starting in Africa after a long crossing of Europe to Athens then by ferry to Alexandria in Egypt. The trip mostly followed the Nile River thru Egypt and Sudan to Uganda and broke in Nairobi before heading further south. The Nile trip was much shorter at ten weeks as opposed to the western Trans Africa at 22 weeks to Nairobi.
Since 2006 a few companies have offered overland expeditions from the UK to Australia. Originated by Exploratory Overland Expeditions  in 2006, the expedition is marketed as the longest trans-Asian overland journey available.
The longest overland expedition of any kind is run by African Trails  their London-Capetown-Istanbul journey (43 weeks) remains the classic overland expedition for die-hard travellers.