Public Transportation, or Transit, as it's more commonly known Stateside, is the integrated (hopefully) system of buses, trains, trams (or trolleys) and other multiple people movers.
The term "Public" implies that it is provided by a Public, or government, body. This fact distinguishes Public Transportation from Paratransit, which could be any of the above modes, but is provided by a private company, usually to transport their workers. Paratransit becomes important in countries where the Public Transportation system is poor, or where workers require additionally subsidised transport (such as blue collar workers in Gulf states) or work night shifts when Public Transportation is either closed, infrequent or unsafe.
Public Transportation works in different ways in different countries. And you can take that sentence in different ways too. In some countries, usually Socialist or leftward leaning countries, Public Transportation operates well (though nobody is ever satisfied). You can get where you want to, when you want to, often faster than you could in a car, and usually with a lot less fuss (ever tried to find parking in London? Good luck.)
More Capitalist or rightward leaning or developing countries usually have inferior Public Transportation systems. The simple reason for this is that Public Transportation is expensive, and its hard to justify the expense. You could probably buy yourself a nice limo or Ferrari for less than the average out-the-box double decker bus. Railway lines cost heinous nine-figure sums to build, and almost as much to maintain. Trams are the new vogue around the world. Light Rail (as they're also called) is as its name implies, lighter than a train, the vehicle is sometimes remarkably close to a bus, there is less pressure for them to run on a segregated track (in other words, they can share the roadway with cars), and they're cheaper.
Government purse strings are getting tighter these days. Governments traditionally get better loan rates from banks because they can just raise taxes when they get into financial difficulty, so long as they lend internally and are not crippled by a collapsing economy and foreign exchange loans. Still, they are now loath to take the financial risks in these heady days of mass media, where mistakes are harder to cover up. What is happening in countries such as Britain nowadays, is the glorified Public Private Partnership, in which the government provides a private company with a guaranteed monopoly on the particular transit service, in exchange for the private company sticking their neck out on the financing. Of course it all blew up spectacularly in Britain in 2001/2 with the collapse of Railtrack, which resulted the then Minister for Transport, Stephen Byers' resignation.
Public Private Partnership works rather well in roads and buses, however. Every time you pay a toll, you're using a road built by private finance. They're remarkably successful and you can see why governments are eager to extend the concept to more expensive rail schemes. The stakes, however, are considerably higher, and there is a big difference in they way people perceive motoring costs versus transit costs.
In the sanctity of your own car, you feel in control. This feeling of control leads you to accept higher accident risks, tolled roads, expensive parking, congestion and pollution. You feel that by being in control of your own destiny: you have the right to choose which route you take, where you park, when you travel, your comfort whilst travelling, and so you accept levels of service you would not tolerate in a Public Transportation vehicle.
Riders on Public Transportation have a notion that the government should provide. You feel you have the right to turn up when you want to travel, and a train magically appear, with a free seat. You get irate if the bus breaks down and you're buggered if you're walking that extra 300 yards to the stop round the corner that has the quicker bus route. Buses smell, trains are infrequent, trams are often overcrowded. This is because they are expensive to run and maintain, and cost effectiveness demands that there is a group of people waiting to be picked up rather than lots of stops for few people. The heightened safety that you demand means that there must be a considerable time gap between vehicles on the railways to avoid collisions and stop delays being passed on from one service to the next.
Public Transportation works best in areas with dense land use. Inner cities, with lots of high-rise offices, or dense residential neighbourhoods (apartment buildings or terraced houses), for example. Texan-style urban sprawl is not conducive to an efficient Public Transit system -- you can't put stops on every corner, so people have to travel longer distances to the stops. In a sprawl situation, the population catchment required for a station covers an area with its limits beyond comfortable walking distance. Comfortable walking distance is relative, of course: based on what people are used to (10 minutes in London is standard, would an average American tolerate walking 10 minutes? Probably not unless they were on a treadmill at their local gym!) and the weather conditions. In Dubai in summer, 100 metres can seem like a marathon.
So is there any hope that your neighbourhood will soon proudly sport a Public Transportation mode that takes you conveniently from A to B without going via C, D and E or taking too long? Maybe.
Buses are easier, but they perform poorly in congestion unless they have well-policed, designated bus lanes that don't suddenly disappear every time they meet a spatially constrained junction. Buses can be small (but remember that they need to carry enough people to justify the driver's salary) and can take circuitous routes through neighbourhoods. If they aren't protected from traffic congestion, however, reliability and journey time go up the pole, and users quickly switch to a different mode. Short, regular feeder bus routes linking wider areas to train stations (faster modes) are a saving grace.
Trains are the Holy Grail, but are under stick because of their cost. I personally marvel at the ability to travel from Brighton to London in under 50 minutes. (Try doing that in a car, sucker!) I am truly awed by how a train travelling 120mph can derail, hit a tree, and only two people die. (Try doing that in your car, cowboy!) Accidents happen, so don't tell me "the train shouldn't have derailed though". Europe is moving towards high speed rail between cities, which is stiff competition for airlines and has boosted the economy in many a town receiving the upgraded service, thanks to the improvement in accessibility.
Trams are the catwalk children of Public Transportation: they're young, sexy, quick, reliable, can operate driverless (like the Docklands Light Railway) and as I mentioned previously, cheap. Companies fight tooth and nail for the right to build and operate them, and they're very attractive for cash-strapped Local Authorities. Unfortunately, many are not quite the success of some of the supermodels like DLR and Croydon Tramlink.
The reason for this is that Public Transportation schemes, historically, are expected to pay for themselves. Road building schemes are a sunken cost, justified by the "congestion relief" they bring (all those time savings multiplied by the monetary value of time spells big bucks) and not to mention fuel levies. This is because more roads breed more traffic, which means more cars bought, more petrol sold, more taxes brought into government coffers. Roads schemes are also quicker to build and therefore less risky (less time for costs to spiral out of control). Another factor is that it is easy to predict road usage: Field of Dreams theory works here.
With Public Transportation schemes, things are a little different. You need to locate the stations close enough for easy access, but not so close that the stops get annoying and waste time and energy. A few errors with the numbers, and you're not recouping that huge investment. Mostly, though, sunk cost is seen as subsidy, where road maintenance costs are not.
As research continues into quantifying, in monetary terms, the value of accessibility, pollution, global warming, that endangered bird whose only remaining habitat just made way for a six-lane superhighway, etc, then Public Transportation schemes may start to fare better in Cost Benefit Analyses.
Until then, practise sustainability: chose the smallest fuel consuming transport mode possible for your trip. If you can walk, walk. If not, can you cycle? Ride a bus? A train or tram? Get a ride with someone who's already going? Maybe you should get a little moped or scooter? You really gotta take the car? Okay, but leave the 12 cylinder gas guzzler in the garage, please, my asthma's getting worse and I don't need your fumes hurting my lungs more, I still wanna use them for a couple more decades. Thanks.
Related topics by the same author: Traffic Engineer.