Smog, congestion and cost: Travelling in a dense urban environment can be a stressful situation at the best of times. Things are changing, however, with more and more environmentally friendly options on the table for those looking to get from A to B. Here, CNBC's "Sustainable Energy" takes a look at five options that could help to green our cities.

Getting around a city or town on two feet has both environmental and health benefits. Walking is emissions free and can, among other things, help people lose weight and boost their mental wellbeing. It's also worth noting that you don't have to pay anyone to walk to work or anywhere else.

Cycling is a popular form of transport in many cities around the world. Cycle hire schemes are becoming increasingly common and efforts are being made to build dedicated cycle lanes separated from cars and other road traffic.

Like walking, using a bike is an emissions-free way of travelling and can, in some traffic-clogged cities, be quicker than taking the bus or train. The health benefits of cycling are also impressive: a low impact form of exercise, riding a bike can boost cardiovascular fitness and aid weight loss.

Buses, traditionally fueled by gasoline, are changing. The Scottish city of Aberdeen, for example, is now home to a fleet of hydrogen-powered buses, while more than 10,000 electric buses are ferrying residents around the streets of Shenzhen, in China.

As the technology that powers electric and hybrid vehicles develops, various forms of transport are embracing change. There are now electric versions of London's world famous black cab, for example. By the end of next year, all cars on UberX in London will either be 100 percent hybrid or totally electric, while no diesel vehicles will be on the app.

The Colombian city of Medellin opened its Metrocable system in 2004, and other cities, many of them in Latin America, have followed suit. Apart from the fact that a cable car's route is both picturesque and uninterrupted, there are other benefits.

The Bartlett Development Planning Unit, part of University College London, has stated that the "speed and comparatively low cost of construction, and low levels of particulate emissions of aerial cable-cars, are part of their appeal in dense and hilly urban areas."