ABOVE) Fanciful diagram of routes through space.  Ships will travel between major nodes where initial velocity is applied.  They will fly-by far more than just a few stars between nodes. It's just too hard to make a more elaborate diagram and fit it on a web page. This drawing gives you the general idea.  A ship could leave Node 1, brake into orbit around Node 2, be refurbished and propelled to Sol or Node 3. Eventually it gets back to Node 1 and is propelled through the great circle, more of a great triangle, again, or it is sent to Sol from Node 1 or back to Node 3 depending on need as determined by long range planners.  Ships could travel from Node 1 to Sol to Node 2 or 3 and back. Several possibilities exist within this arrangement.  Regular routes could be maintained, like buses, or there could be more flexibility in the system depending on the needs of travelers.  Interstellar flights would be booked years in advance and light speed communication by radio or laser can stay ahead of the ships.  We tend to think of our solar system as being central to the beam rider network, but in time there will be populations in other star systems and more travel between other star systems than there is between our own solar system and neighboring stars. We also tend to think of Sol as the major node of origination and beam rider routes branching out from Sol with ships flying outwards and returning when in reality they might leave our solar system, reach a distant terminal node and then be sent by way of a route that doesn't even come near Sol but ends at another distant node.  Many ships might originate at Node 1 when our AI robots have developed other star systems, a bright A type star like Sirius pictured blue in the diagram and just fly-by Sol on their way past many star systems on their way to another node.  Interstellar traffic will actually be a complex matter controlled by enhanced humans and computers of the future. Interstellar communication networks will also be a complex affair. 
INTERSTELLAR TRAFFIC
ABOVE: We've alread seen that ships can be deflected in three dimensions.  Previous diagrams showed arrangments that could only deflect ships away from a star. In the diagram above we are looking down from the y-axis into the x and z planes.  The beam rider stations are in stellar polar orbits perpendicular to the path of the ships and the ships are using the star's gravity and magnetic field (Dr. Zubrin says mag-sails can adjust "lift" and even use the sails to pull towards a star) to deflect towards the star and the beams are deflecting the ships in a more "starward" direction which will require tacking with mag-sails until they are at a greater distance and can catch the beams more directly. Distant mass beam stations in long slow orbits powered by mw beams or lasers from stellar energy complexes assist the maneuver. 

This takes me back to earlier comments about somebody else running with this ball much further than science fiction writers and game creators would ever want to.  First of all, delineating routes through the galaxy and determining 3D deflections at each star would be an amazing feat. I've only done a little calculating for 2D deflections.  Allowing for relativity, losses due to tacking, the effects of other star's gravity, even drag in the interstellar medium and drag encountered by passing through a star's heliosphere (something I thought ships should avoid) as well as speed picked up when ships are moving in the direction of a star's wind, determining times of fly-by, the effects of beam dispersal, and other factors would be a great achievement worthy of real pros, master's or doctoral theses, and publication in respected academic journals.  Throw in some realistic design proposals for mass beam projectors and power systems and what a tremendous work that would be! 

ABOVE: Another thing that we or at least I tend to think in terms of is an ever expanding bubble of human colonization.  In reality we may see bubbles containing beam rider networks growing to a certain limit, perhaps a 50 ly radius sphere, and then more bubbles of replicating robotic development and human colonization growing.  Some will over lap.  More of a cloud rather than a sphere of colonized space may emerge.  Given the limited lifespans of genetically enhanced humans even and the velocities of star ships, people of other star systems would be limited to travel within their local bubbles and beam rider networks would exist within each bubble although some would cross over into other bubbles.  One reason I tend to think of this pattern is that it would seem logical to send replicating robots out to a central location beyond the limit of the first bubble where they then expand outward to form another bubble of developed space.  The bubbles probably would not have nice spherical shapes either but be somewhat irregular depending on the locations and types of star systems of interest.  Instead of a sphere of human and robot expansion into the galaxy we will see more of an "amoeba of influence" or growing cloud of robot developed systems and human presence.  Really rugged pioneers might take their ships to great distances and start clouds of expansion way beyond the main cloud that eventually merge.  Just some thoughts. 

How would ships be shielded?  Perhaps they would be coated with diamond hard carbon derived materials and use magnetic scoop shields that can deflect or "inhale" particles in space without too much drag.  Shield vehicles could also be used to take the brunt.  Certainly they would require advanced LSS technologies and materials to last on the inside as well as the outside if they are to be self contained vessels for decades, even centuries. The ships will be made of advanced synthetic materials that never rust or corrode.  There  won't be any steel bulkheads or aluminum ones either.  Perhaps on board nano-manufacturing could be used to maintain and repair systems.  Android crews could do a lot of work to keep up the ships.  I've written about avoiding collisions in space and the use of sectional mag-sail loops repaired by robots on pages in the Starships folder. 

Recently I've read about using smaller masses to act as gravitational tugs to deflect asteroids.  I've also read about propelling asteroids at high speeds past planets to exchange momentumn and alter the orbits of planets.  If it was necessary to correct the course of a starship could another mass be propelled up to higher velocity, race past the ship and trade some energy gravitationally, or could it use its sails to slow down and match trajectories with the ship then let gravitational attraction induce some minor course correction?  And while we are thinking about this, what if a ship's mag-sail gets demolished by a collision and is irreparable?  Could a replacement sail unit be propelled up to about 0.9c, brake in the IM as it nears the ship traveling at 0.3c to 0.5c and be hauled over to the ship and installed by the crew?  If a ship's protection systems fail entirely and it is demolished by collision with a boulder in deep space, the only consolation will be quick death.  Airplanes crash. Ships sink.

Also, what about communication with and coordination of ships and planetary systems?  Light speed communications will be faster than the ships.  Long range traffic planning models based on human populations, growth rates, economic factors, need and want for interstellar travel determined by surveys and reservations made many years in advance by long lived future humans in various star systems could be run in computers to make predictions as well as make plans for booked flights.  Super computers and elaborate tracking and navigation systems will know where ships are or ought to be to guide propulsion beams. 

Rendesvouz with incoming pods and stations in the system ahead as well as outgoing pods and ships at 0.5c should be possible.  The pods will be braked and accelerated by mass beams but they will also have small fusion drives in my vision of things.  Star ships would also have fusion thrusters to maneuver around some, so successful rendesvouz and staying "on beam" should be possible.  If it isn't there could be some stranded space travelers.  If outgoing pods fail to meet the ship as it flys by a star system perhaps they could use their sails to brake in the interstellar medium before disappearing into distant space and rescue vehicles could be propelled out to them.  It seems to me that neighboring stars will be colonized by humans and robots traveling by many other methods before a vast beam rider network for common place two way travel between the stars emerges.  Oort Clouds must be charted in detail and tracking stations will be located in these nether realms of our own and other star systems.  There will be robot inhabitants of the Oort Clouds and possibly micro-black hole powered beam driver stations.  This could make pod journeys safer and there could even be rescue ships and stations drifting slowly in these outer realms. 

This is all really fascinating to me.  Why? Because we can forsee interstellar travel without warp drive and it's really doubtful that the speed of light can be exceeded.  Even sub-light travel requires vast energies.  Given the resources of stars, planets, moons, asteroids, trans-Neptunian type objects, rogue planets, brown dwarfs and comets, space is filled with far more than we once imagined and vast populations could be sustained in space if people in the future want to live out there.  We could also overrun the galaxy in a few thousand years at uncontrolled breeding rates.  People seek new frontiers for many reasons.  One of them is the search for new markets.  Where civilization has been entrenched for a long time all the business is taken! Unless you can come up with an all new product, a cheaper product of equal or superior quality or marketing strategy or an old business giant dies, there's too much competition.  Out on the frontier there are people needing everything imaginable and more.  As pioneers head out for whatever reasons they have, some people can get rich selling them food, spacesuits, transport, etc.  What if nobody wants to leave the Earth and humans stabilize and even reduce their numbers?  Will our space dreams evaporate?  Will space just be a nice place to visit but nobody wants to live there?  I can't imagine genetically enhanced humans with lifespans of several centuries resisting the lure of outer space.  Also, if given room to breed some people are going to breed until they run out of room.  Some will say "too hell with breeding" and others will move out to virgin territory.  With the possibilbities of robotics and vast unclaimed natural resources there are going to be people who take advantage of the frontier.  Life on Earth could become utopian; however, there will be people who seek new horizons.  Earth could become a glaciated planet hostile to technological civilization also. If the space future is nothing but a dream, it's a very exciting dream in the here and now.