GPS for Bikes in the city

Question
My son drives to cities like NYC, Philadelphia, Boston, Washington. He parks the car, then bikes around. Locating intersting sites, then returning to his car can be time consuming and distressing.

What GPS devices do bikers rely upon and why? Can you direct me to reliable sources based on actual experience?

Issues would be voice directions from the GPS, battery life, size and weight, reliability, etc.

    thanks for your help.


                 Steve

Answer
Good to hear from you, but I haven't had any personal experience with GPS.  In theory, I know a bit about it, but don't know which brands are best.  I did an advanced Google search for documents with both the word GPS and the word bicycle.  Got quite a few pages with product reviews and so forth.  

Thinking about things in theory, the city map data would be a big issue.  GPS basically just gives latitude and longitude numbers.  Also, possibly, elevation.  The route one goes depends on street and path layout in the city.  Main problem is, most maps and data overlays are likely for cars.  The best way to get from point A to point B is different for a car than for a bike.  For instance, in big cities, a car map might put one on a freeway that would often be illegal for bikes.  Also busy arterials in a city can be bad if there is no shoulder or bike lane.  At the same time, there is often a quiet residential street that parallels the busy one.  A better way for bikes.  

In a city, I use a combination of quiet back alley type residential streets and bike trails.  Some cities offer special bike maps of the city.  

I guess GPS users can leave bread crumbs, so to speak and have the unit remember where they went.  Then they can retrace the steps.  One can make their own bike maps that way.  I think there are some web sites and groups where people have shared these itineraries.  Also local bike clubs might have people with GPS experience who share ideas.  

Basically, I haven't used GPS yet, but did some Google research.  

The topic of "bike route data base" interests me as it would be different than standard instructions for cars.  Bike data is often not available or comes from many divergent sources such as park guide trail maps, specific maps for one recreation trail or, if one is lucky, a bike map of an area.  Many cities offer bike maps.

Hope this helps some at least.
Robert
http://www.theslowlane.com