CartoType calculates transcontinental routes on mobile devices in well under a second. It can use mapping data from any source, including OpenStreetMap and ESRI shapefiles.
Here is a route across densely-populated Southern England from Basingstoke to North London.
Let's zoom in to the start of the route...
...and the end of the route:
What about one-way streets? Here are two versions, eastbound and westbound, of the same route in Central London, showing how CartoType obeys routing restrictions. Arrows show the direction of the one-way streets. The style sheet gives complete control over the appearance of all map symbols, including these.
eastbound:
westbound: