The Philosophy of the RHW (RealHighway) System

As many readers of this blog may know, I’ve been a part of the NAM Team for a number of years now (this next February will mark 7 years), and one of the main projects I’ve been involved with as part of that is the RHW (RealHighway) system. The “R” in “RHW” has stood for “Real” for a few years now, but way back then, it stood for “Rural”, a makeshift designation that the developers quickly found inadequate, but lingered with the general public for some time. At that point, the only release was a public alpha, brought to fruition by qurlix, which functioned as little more than a proof-of-concept. It had only one network (known today as the RHW-4), no interchanges, there were at-grade intersections with just Streets and Rails, and only two puzzle pieces–one to allow the NAM Elevated Road Viaducts to cross the RHW (but not One-Way Roads or Avenues), and one to allow GLR to cross at-grade (there was no draggable GLR in those days).

The RHW has come a long way since those days. As of NAM 31.2, there’s 33 networks of all shapes and sizes, hundreds of puzzle pieces, and thousands of draggable possibilities. Which, understandably, is why one frequently runs across players new to the game or to custom content, who become exasperated with the seemingly large magnitude of the system, and make comments to the effect of “I don’t get it.” This post is partly intended to clear up what the RHW is about for those new to the system, and also to briefly go into what the RHW will look like in the future.

The Purpose of the RHW System

At its core, the RHW is designed to be a variable-width highway system, with modular interchange functionality, and some semblance of real-world scale. This is in sharp contrast to the default Ground and Elevated Highways–often called “Maxis Highways”, or “MHW” in the community–which operates at a fixed width (6 lanes in 2 tiles–no options for more or less), uses a limited set of stock, pre-fabricated interchanges, and is compact to the extreme, being half-scale with respect to all other transport networks in the game. (Consider that the 6 lanes of the MHW fit in less space than the 4 lanes of an Avenue.)  The game’s designers intended a scale of 1 Tile = 16 meters on a side (that’s about 52 feet, for US/Imperial unit folks).  Given that the MHW model takes up only about 18m in width for the full 2-tile-wide span, it means that its lanes are 3m (9.84ft) wide–less than the typical standards for a residential street here in the US, The connection ramps on the MHW/Road interchanges are a mere 48m/156ft. long, which is also about half-scale.  The shortest ramp of this type that I could find in my local area was the I-84/39th Ave (Cesar E Chavez Blvd) ramp in Portland, OR, which is about twice that.

When the RHW was first coming to be, the most requested items in the old “NAM: Requests” thread on the Simtropolis Forums were new interchanges for the MHW. People were clamoring for new ways to hook their highways up to their surface street grid, and to join multiple highways. The problem, however, was that making new interchanges was an extremely difficult task, taking a team of people several months to make just one interchange. At that time, aside from the various “tweaked” versions of existing highway interchanges, there had only been 2 completely custom, fully-functioning interchanges completed for the MHW system: the Orthogonal x Diagonal Interchange (released in NAM Version 4, in 2004), and the Ground/Elevated Stack (added in NAM 15, in 2005).  There’s only 5 now, and the third took nearly 2 years of development. The modeling process required for 3-dimensional NAM items is completely different than the process for creating buildings for the game, and the people with the facility and time to do it have been few and far between. The old NAM: Development thread, also at Simtropolis, features dozens of pages littered with MHW interchanges people started and never finished–it’s an “interchange graveyard”, of sorts. My colleague Haljackey (who you may know from his excellent SC4 YouTube videos) has done some archaeology on this front, and posted the results in his SC4 Archives thread at SC4 Devotion. Some folks who were really desperate for more options would just use truncated one-sided MHW-to-One-Way Road ramps, and fake the connections using One-Way Roads, but these creations were rather ungainly, to say the least.  There were also a number of users back then who had been experimenting with the idea of splitting Maxis Highways into “multi highways”, to have wider medians or build collector-distributor setups, using a trick developed by Simtropolis transit theorist lakeyboy, as demonstrated by three editions of “Lakeyboy’s Multi Highway Guide” back in 2004 (which, if you’re up for a little history lesson, can be found here).

The RHW system was really a clean slate.  The small but ardent userbase its public alpha was attracted to it due to its more realistic scaling, and the ability to separate the two sides of the highway without the “multi highway” workaround.  I was part of that userbase.  And we were all clamoring for a way to build proper interchanges with the RHW, rather than making abrupt switches over to MHW, or resorting One-Way Road kludges.  This was what got me into transit modding, roughly a year after the RHW alpha.  When I first started looking at solutions to the lack of interchanges, I initially considered building standard prefabs for the RHW.  However, I decided against this, for a couple of reasons.  The RHW userbase–myself included–wanted a lot of flexibility in interchange design.  We were all intrigued by the possibilities of the Kurumi Field Guide of Interchanges, and wanted to replicate that in SC4.  And it was extremely difficult to ignore the overwhelming record of failure in creating new Maxis Highway prefabs.  Making RHW prefabs would have been no different, and given how much innovation the RHW system has driven within the NAM Team, the trajectory of further NAM development and of SC4 custom content in general would have been a lot different.

So, I took advantage of the clean slate, and began detailing plans for the Modular Interchange System, or MIS.  That’s where the term for the one-lane ramp network originates, in case you’re wondering.  Instead of building full interchanges, the premise was to build pieces so the user could assemble their own custom interchanges.  Going modular shifted the burden of interchange construction from the developer to a public that was eager to play highway engineer.  Indeed, almost 6 years after the MIS debuted in the RHW 2.0 release of January 2008, requests for new MHW interchanges come maybe once a year (and almost always from the same individual).  Instead, users lined up in the RHW development thread to request new ways of connecting their RHWs into the MIS–far more manageable requests.  As the RHW’s variable width functionality, which qurlix had first proposed in 2006, came online, rather than having to make a whole slate of new prefabs, all we had to do was make a few new on/offramp pieces, so users can hook the new networks into their existing interchanges after a widening project.  And until I mentioned it here, I suspect many of you had never heard of multi highways (or, for the old-timers, had long forgotten them).  The reason for that, of course, is the RHW.  In that regard, the RHW philosophy has been a stunning success.

Let’s look at the basic breakdown of how this has been accomplished with the RHW, by examining the types of pieces that fit together to create highway systems:

Starter Pieces: The network the user gets when dragging out the RHW Network Tool is the two-lane, two-way ground-level network known as the RHW-2 (which stands for RealHighway, 2 lanes), which looks like a Road with shoulders.  The other 30+ networks are built using starter pieces–these are basically special little stubs that convert the default RHW-2 network into other widths and elevated heights of RHW.  To accomplish this conversion, either start with the starter, and drag the RHW-2 network through it, or place the starter over an existing stretch of RHW-2 (though you’ll have to redraw the RHW on one side of where you placed the starter).  Starter pieces are ubiquitous with many NAM options, and they’re really the bread-and-butter of some of the mod’s most innovative features.  It’s also worth noting that tiles in the immediate vicinity of a starter piece may sometimes be less stable, so don’t try to get too fancy near it, because it might not override to the new network properly.

Transition Pieces: These allow for transition between two different RHW networks: there’s a wide variety of pieces allowing for transitions between different widths or different heights.  Many of the newer height transitions–both the standard variety and the “On-Slope” transitions–are built using the FLEX transitions, which are overrideable and will generally conform to match the networks connecting into them.

Ramp Interfaces (On/Offramps): These are the ramp branches/on/offramps that allow you to make interchanges with the RHW, and start the connection from RHW-to-Surface Street, or into another ramp interface, on a different RHW.  The stub on the end of the ramp branch can then be dragged or otherwise connected into that surface street (e.g. a Road, One-Way Road, Avenue, NWM network, etc.), or to a corresponding ramp interface on another RHW.  Ramp Interfaces come in various shapes and sizes, with different angles and widths of branches.  Newer developments on this front include the FLEXRamp system, which is overrideable and conforms to the network connecting into it.  We are transitioning in earnest toward making as many ramp interfaces into FLEXRamps as possible, mainly for the potential to make the process of building and upgrading RHW systems far easier.

Wide Radius Curves: Each RHW network can curve and go diagonal.  The Wide Radius Curve, or WRC, pieces, are plopped over a network’s default curve, and give it a smoother radius.

Fractional Angles: Fractional Angle (FA) pieces allow construction of networks that are neither orthogonal or diagonal.  Fractional options for the RHW, abbreviated as “FARHW” currently exist for most of the ground-level networks in the RHW system (no elevated FARHW yet), at the angles of 18.4/71.6 degrees, known as FA-3 (because it travels 3 tiles lengthwise for every 1 tile on the vertical).  FARHW ramp interfaces exist, as do intersections for connecting FARHW ramps up to surface streets.

Cosmetic Pieces: These are strictly cosmetic, optional pieces, designed to allow you to customize the look of your RHW, primarily with respect to striping patterns for exit lanes, lane end warning arrows, etc.

FLEXFly: FLEXFly, or Flexible Flyover, is a flyover ramp system, a special 1-lane elevated ramp curve that allows various ground-level RHWs to pass under it.  It also has a ground-level cousin, FLEXCurve.  Note that FLEXFly can’t support many newer RHW networks, including many of the new Level 1 (L1) elevated items.

Road/RHW, One-Way Road/RHW, Avenue/RHW, and Rail/RHW Interface Pieces: These allow RHWs to intersect or interact with surface networks in various situations.  The pieces allowing elevated versions of these surface networks can be found under their respective buttons (albeit many of these pieces will become deprecated with the completion of draggable elevated viaducts).  There’s also a few oddities under these buttons: the Road/RHW button contains all the existing pieces for allowing RHW networks to cross over Flexible Underpass, or FLUPs, pieces.  The Avenue/RHW button contains some ramp interfaces for Avenues, in addition to the Diverging Diamond Interchange (DDI) intersection piece, and the FlexSPUI (Flexible Single-Point Urban Interchange) piece.

Notes on Network Types:

Other Things of Note:

  • Many pieces, particularly those dating from the RHW 2.0-4.0 vintage, have starter stubs on the ends.  This was done to simplify usage–for example, rather than having to dig for the appropriate starter piece or build over a pre-existing stretch, a ramp interface could be used as a starting point for building some sort of RHW network.  However, these starter pieces are notoriously slope-intolerant, and the attempts to ease the override situation made the actual engineering of interchanges a good bit more difficult on the terrain front.  Later pieces don’t have starter stubs for terrain-related reasons, and most Wide-Radius Curves never received starter stubs (and never will).  The move toward incorporating more overrideable (and more slope-tolerant) “FLEX” items is partially for this reason, hence the FLEXRamp system, which is still in an infant state at present.
  • Elevated network items require a lot more work to make than ground-level items.  For the ground stuff, all we have to do is make a texture, and sometimes apply it to a flat plane.  For the elevated stuff, in addition to textures, there’s a lot of specialized 3D modeling work.  As a result, only about 3% of all the pieces available at ground level have elevated counterparts.  The elevated counterparts have perpetually been on the drawing board as long as the related ground piece has been a twinkle in a developer’s eye, but it just takes a good long while, and we have quite the backlog on that end.

User-Friendliness, and New Efforts to Improve It

Over the years, there has been a number of users who have complained that the system is too complicated, and that the process of building these modular interchanges is too time-consuming.  A good number of these users have remarked that the like the looks of the RHW, compared to the Maxis Highways, and want the variable-width aspects, but that they find the whole notion of spending 30 minutes building a single interchange excessive.  A few have gone to the extreme of suggesting that we create MHW-style pre-fab interchanges for the RHW, an idea which we’ve vociferously shot down.  With as many RHW networks as there are, and considering that many of these users will be wanting to interface these RHWs with not just the game’s initial slate of road networks, but all of the wider versions of these networks included in the Network Widening Mod (NWM), we’d have to build hundreds, if not thousands, of pre-fab interchanges.  Those very users, who are complaining about complexity and the number of pieces, would no doubt be absolutely incensed if we were to fulfill their request, and they’d have to navigate twenty new menu buttons with 50 interchanges under each TAB Ring.

We have, however, hit upon a way to extend this sort of convenience, without sacrificing the successful philosophy that has allowed the RHW to flourish.  This new development is known as QuickChange, and I recently unveiled it as part of a livestream event, which has since made its way to my YouTube channel.

The name is effectively a portmanteau of “quick” plus “interchange”.  QuickChange basically combines all the basic pieces required to build the connection from the RHW end into a single piece–a ramp interface, plus any required transitions.  However, this single piece is completely constructed from multiple, smaller FLEX components, so it’s overrideable, and one piece can work for any network that has ramp interfaces, and like FLEX components can actually be swapped in to replace the ones included by default in the QuickChange (particularly on the ramp interface end).  And because the connection at the end of the transitions doesn’t have a preselected network attached, one piece can connect your RHW to any number of surface networks (or other RHWs), allowing one single QuickChange to work in a mindboggling number of situations.  The initial estimate is that we’ll be able to allow users to construct just about every basic interchange type they’d desire with only a couple dozen QuickChanges.  The Partial Diamond and Parclo Inner Loop QuickChanges will be available in NAM 32, and we’ll continue to develop more as the NAM continues on into the future.



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