The idea of a city vacation may conjure up images of treeless sidewalks and traffic-choked streets, but several US cities get high marks for environmentally friendly initiatives.

The idea of a city vacation may conjure up images of treeless sidewalks and traffic-choked streets, but many urban areas are actually quite “green”.

Public transportation systems cut down on automobile carbon emissions, bike lanes are as popular as cupcake shops and city officials are cutting costs by upping energy efficiency. Plus, travellers can often take public transport to get there. In honour of Earth Day (22 April) in the US, here’s a look at five American cities that fit the bill for an eco-friendly trip.

Portland, Oregon
This city is accustomed to finishing in first when it comes to being green. This year, Portland topped the list of America's greenest cities, voted on by the readers of our content partner, Travel + Leisure magazine. The city has a whopping 288 parks, and a quarter of Portland is shaded by trees. The city is also well-known for its cycling culture, with 318 miles of bike lanes and off-street paths. Portland also got top billing on the Mother Nature Network’s green cities list, which looked at the city’s carbon footprint, including its recycling efforts, air and water quality, LEED-certified buildings, green space and use of renewable energy. Portland’s Climate Action Plan encourages both the city and its residents to reduce carbon emissions by greening home energy use and making climate-friendly food choices.

San Francisco
The city on the bay’s eco-conscious vibe runs from the mayor’s office -- which has been pushing solar energy in recent years -- to residents and their well-known green-friendly lifestyles. In 2011, Siemens Corp named San Francisco the greenest in North America based on 31 sustainability factors, such as carbon dioxide emissions, land use, transportation, energy usage, waste, and water and air quality. The city scored big for its low electricity consumption -- spurred by city efforts to install energy efficient appliances and heating and cooling systems, its strict efficiency standards for buildings and its waste recycling program. The city was the first in the nation to mandate recycling and composting in 2009, and it reached a recycling rate of 77% in 2010 . The popular and growing ban on plastic grocery bags also got its start in San Francisco in 2007.

New York City
Known more for traffic congestion and the high voltage lights of Times Square, New York City nonetheless gets plenty of recognition for being green. Why? The city may be jam-packed with people, but its carbon emissions per capita are low. The extensive subway and public transportation systems ferry plenty of passengers, and being without a car in the city may be more the norm than the exception. The Siemens Corp study ranked New York first in green transportation, noting that 37% of commuters get themselves to work without using a private car. The city also has the world’s largest hybrid-electric bus fleet. Biking is big, thanks in part to the city’s environmental policy push, which added thousands of bike racks, handed out tens of thousands of free helmets and installed hundreds of miles of new bike lanes since 2006.. That effort also earned New York kudos from Bicycling magazine.

West Coast cities do well on these eco-friendly lists, and Seattle has been at the forefront of the environmental movement for some time. In recent years, the city announced a goal of becoming carbon neutral, or having net zero carbon emissions, by 2030. Its building standards encourage LEED certification for new construction, and city efforts call for existing buildings to take steps to improve energy efficiency. This port city harnesses the hydroelectric power of the surrounding water – 88% of the city’s electricity came from hydropower in 2010 -- and residents are prompted to install solar panels to power their own homes with the help of federal and state credits. Like San Francisco, Seattle excels at recycling and composting by making it the law. Even restaurants have to provide takeout boxes and packaging that can be tossed in either composting or recycling bins.  

Denver, Colorado
The mile-high city puts its environmentally friendly stamp on various facets of life through the Greenprint Denver program. The city sprung for solar panels and new LED bulbs for traffic lights in 2010, saving money on its electric bill. Its 105 miles of bike trails and lanes are populated by riders using a city-wide bike-share program. Beyond cycling, the love of the outdoors is fed here by more than 200 city and mountain parks. If that’s not green enough, the city launched a major initiative to plant 1 million trees by 2025. The Mile-High Million program encourages residents to register their recently planted trees, and the city is already a quarter of the way there, according to the “current tree count” on the program’s website.

Lori Robertson writes the Ethical Traveller column for BBC Travel. You can send ethical dilemmas to