Urban Fieldcraft is a totally legitimate area of study.
I've spent a lot of time living abroad, as well as having lived in 8 different States in the US, from the cement jungles of Southern CA, to the Coast of Maine, as well as Georgia, Virginia/DC Area, Pacific Northwest, North Carolina, Colorado, and Utah (this is my 3rd time living in Utah). I've spent a lot of time on the road, to include work that involved 6 and 7 day weeks of basically living in a car, and watching specific addresses, vehicles, and people.
I've mingled among crowds in Tokyo, Seoul, Munich, Bern, Amsterdam, Paris, London, Moscow, Tallinn, Helsinki, Stockholm, Panama City, Mexico City, Guadalajara, and many others.
Fundamental Principles
Biggest takeaway for me in an urban environment is the same as in the woods, mountains, or jungle: Listen to your sixth sense, feel the surroundings, pay attention to the local animal life, and behave accordingly.
That is as true as when I'm walking down the boardwalk in Santa Monica and some hardcore criminal gangsters are out fronting, as it is when hitching a ride in Moscow or Sainkt Petersburg. Same thing applies when something tells me not to walk another step in La Jungla, because there's a 13ft alligator in front of me that just popped its eyes up out of the water to scan its sector after feeling something big resonating the water around it, indicating a possible mealtime.
Lessons from bums
One group of people I always pay close attention to in urban settings are the homeless. What specific practices and approaches do they use to survive every night, and how do they avoid confrontations with human predators that are often found among their own?
What type of shelter and transportation do they use in the different seasons? Where do they retreat to at night? How do they dry off if it has been raining hard?
You have it made if you are homeless in the US. There is plenty of food to eat that can be had when wasteful people throw it away, or offer you some.
Public restrooms are magical, in that they often have these shiny things on the wall that you can place your collar up to, and blow hot air into your clothes, permeating the room with your stench, but drying off nonetheless. They are like a public clothes dryer for on-the-fly, field expedient use if you are homeless.
Cardboard ground mats are common in the US, although many homeless have upgraded to camping mats for sleeping. Money for all your basic needs is easily obtained working a corner, so that you can have daily spending cash for food, clothing, and survival items. Shopping carts are plentiful for semi-nomadic transportation of your personal effects, and can be improvised to constitute a part of your shelter, especially when it is windy.
Being homeless in an underdeveloped nation? That's a different ballgame. Police and security forces work hard to keep you away from economic activity zones, so children are often used as surrogates to panhandle and pickpocket. You will see major pickpocketers in Southern Europe, as well as throughout the rest of the developing world.
Foreign Business Travel
Again, situational awareness and listening to that inner instinct of survival will guide you through high threat areas. Kidnapping is common in many places if you're on a business trip, so I recommend that anyone who travels in developing nations for business to get quality training from people who specialize in plainclothes overseas living as a foreigner with a solid military or intelligence background, and not from any of the 3-letter agencies you commonly hear in the news (they are often tourists on vacation in a diplomatic community with no real exposure to the ground truth of the nation they are assigned).
Biggest thing that anyone can go and do right now is learn how to drive a manual transmission, Asian or European-built small sedan, if you are going to be traveling a lot in developing nations. You should also do an area survey/area study, and start learning conversational phrases in the local language, as well as important social and cultural traditions and taboos.
US Urban Areas
In urban areas in the US, you typically have areas of major metropolises that you don't want to go into. You can look at crime maps of pretty much any city in the US, and then establish control measures using prominent features that divide a city.
Historically, this has often been based on which side of the railroad tracks you were on, or how high in elevation different neighborhoods are. Property values increase with elevation because of the view and exclusivity of those neighborhoods. Neighborhoods next to industrial complexes where there is bad ground water, higher pollution, and higher noise are often the areas with higher crime rates. Look at your major arteries of the city, and stay on the ones that avoid these areas if you are looking to minimize the risk of being victimized. This is a good approach for home buying and tourist travel.
The reality though is that if you are working, you're going to have to go where you need to go, often to industrial centers. One of the best things you can do is keep 1-2 car lengths in front of you as best as possible, and have several plans for what you will do at intersections where hoodrats like to prey on people. I personally carry and have spent a good part of my life training to shoot in, around, and from within vehicles, as well as use vehicles as a quick escape platform, or a weapon.
I cannot recommend getting some good offensive-defensive driving training enough. The Secret Service and US State Department Diplomatic Security Services have some very good training programs for this, as do a few units within the military. There are a few trainers around the Country who do this type of training.
I would also recommend finding a reputable trainer who has a lot of experience with shooting from within vehicles, how to mitigate the dangerous effects of initial glass perforation in the car, and has a comprehensive program for dealing with shooting your blind spots. Any time I get out of a car, I'm expecting someone to come from my rear where the blind spot is.