Interstellar Highway

To think that we conquered space so! We look at the stars and see not individual dots in the sky, but a vast web of roads. The universe is that much closer.

— Percy Grumont, Highway Mechanic

The backbone of human spacefaring, the Interstellar Highways are a complex network of 'roads' between stars, shortening light years into mere weeks of travel. Maintained by thousands of workers across hundreds of solar systems, and expanding out further into space, the network is one of humanity's great projects.

Functionality

Interstellar Highways are essentially light-energy tunnels carved through space, within which speeds are increased and distances are contracted. These factors allow for significant pace across light years, with some variance over distance travelled and a ship's individual capacity, usually between 4-6 days per light year.
Highways require multiple components to maintain and be used:

Hardlight Generators, which create the boundaries of each highway

Relay Stations, also known as Pylons, which guide the highway through space to maintain integrity

OnRamps, which enable ships to enter the highway at high speeds in a controlled manner

Generator

Usually installed at the boundaries of a star system, hardlight generators create the walls of the tunnels through space, as well as controlling the area inside to create optimal conditions for transit. Expensive and cumbersome, these are highly staffed by specialists and unquestionably off-limits to civilians.

Pylon

Placed at regular intervals along the highway, as well as in large quantities at any junctions or branches, relay stations help to maintain the structural integrity of the highway, as well as handling communications through space. There are always more pylons than necessary, allowing for the highway to continue operating if a few malfunction.

OnRamp

Now installed at the boundaries of star systems, OnRamps facilitate entry onto the highway. In layman's terms, they 'slingshot' ships into the tunnel, allowing them to reach cruising speeds sooner, as well as having a hand in managing the flow of traffic. These usually have stations attached to handle a system's trade and commerce.

History

As humanity stretched farther into the stars, developments in FTL technology struggled to maintain connections between systems. Ships couldn't travel quite fast enough, limiting the transport of goods and people across the galaxy. In hopes to improve trade, the Universal Government promised significant funding to anyone researching solutions, ranging from improved engines to teleportation.
The project that ultimately developed Interstellar Highways arose from a lesser-funded exploration of nascent hardlight technology, which discovered distortions within enclosed hardlight spaces. With further tweaks, they determined that these distortions consistently reduced the effective distance travelled within a tube, and the researchers quickly set about applying this concept to transport. After a proof concept highway was established in an under-travelled section of the outer solar system, the Universal Government approved it for deployment throughout occupied space.
The network has undergone a systematic expansion and upgrade process over the centuries, including a total replacement of the initial connection between Sol and Alpha Centauri, and the construction of new branches and OnRamps throughout the galaxy. Improvements in hardlight generation increased the rate of distortion as well as increasing structural integrity, and the quick access to resource-rich systems helped bring down construction costs.

Network

Given the three dimensional nature of the highways, mapping the entire network on a 2D plane is considered something of a fool's errand. Maps will generally focus on individual routes and relevant branches, more akin to old train diagrams.
When it is represented at a larger scale, it is shown as a great burst of lines streaming out from the Sol system in every direction. There is an as-yet incomplete ring of highways that allow for bypassing this central location, and as FTL technology improves it is likely more bypass routes for busy 'junction' systems will be built.

Frankly, navigating the Sol System is abysmal these days. Most spaceflight has to be done entirely by radar, because any navigational aids are made silhouettes or rendered invisible behind these massive glowing tentacles. Not to mention the traffic!
When sailing the stars became trivial I doubt NOSA or whatever thought we'd have traffic jams out past Pluto most days.

— Frank Casey, Mars, Sol

Skip

Before the wide scale adoption of the highways, and subsequent FTL developments like Motrium Warp Drives, every star was important. Whether it be for resources, sightseeing, or the ability to stop and refresh, travelling to distant reaches would necessitate stopping at every system on the way.
This isn't true anymore, and systems like Dumas are being left behind by the very technology they begged to be built.