Road construction
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A particularly conspicuous fact of all games I've seen is that they often provide significant information on the cost of building structures, vehicles, and other units, but rarely—if ever—provide realistic estimates or actual figures on the costs of various engineering projects, including roads, bridges, tunnels, raised highways, above-ground ramps, supported landing platforms, and the like.
This article is an attempt to quantify the costs of building ground-level roads and highways. Elevated causeways, bridges, tunnels, and other projects are in forthcoming (?) articles.
Vehicle standards
Passenger vehicles in the 20th and 21st centuries on Terra were designed to be between 1.5 metres and 2.0 metres in width, with a length anywhere from 2 to 4 times their width. Larger transport vehicles reach as large as 2.6 metres in width and up to 25 metres in length, which is defined by many governing bodies to be the absolute limit.
The average passenger vehicle weighs between 1.0 and 2.0 tonnes. Larger, heavier vehicles begin to gain prominence as technology and affluence increases, although environmental concerns over fuel consumption, pollution, and the safety of other road users usually serve to limit passenger vehicles to an upper extreme of 3.0 to 4.0 tonnes.
Road life
Roads are rated for a certain number of vehicles per day. The thickness and type of the pavement material and the width and support of the road both serve to increase how long the road will last and to reduce wear and tear on the vehicles making use of the road surface. Roads that are built well in excess of the actual usage are cost-inefficient. Roads that are built too spartanly for the actual usage suffer significant damage and require frequent maintenance to repair cracks and damaged sections of the road surface.
The damage a vehicle causes to a road surface is considered equal to the fourth power of the vehicle's mass in tonnes. Thus, a vehicle which weighs 1 tonne causes one-sixteenth the damage that a 2-tonne vehicle inflicts to the road surface. A large long-hauling transport truck weighing 16 tonnes inflicts nearly 100,000 times the damage that a 1-tonne passenger vehicle inflicts.
Since passenger vehicles rarely exceed 3.0 tonnes, there is little concern over the amount of damage that passenger vehicles inflict in comparison to the larger transport vehicles; in general, passenger vehicles are considered to cause negligible damage to Pre-Stellar road surfaces, although a surface which exclusively receives passenger vehicles will still deteriorate slowly.
Roads are typically constructed with an expected lifespan of 40 years, meaning that the entire pavement surface will require teardown and replacement after that span. Specifically, roads are built, then maintained until the cost of maintenance for the next 40 years would exceed the cost of replacing the road surface; once the projected cost would exceed the cost of replacing the road, the road is replaced. Roads which require replacement sooner than 40 years were built improperly, and roads which require replacement later than 40 years were built too expensively for the conditions. Regular maintenance of a road surface is always mandatory, although maintenance amounts to filling "pots" in the road surface and sealing cracks only.
Road types
There are several road types.
Lane
A lane is a pad that is three metres wide and an arbitrary length. A three-metre wide lane is actually at the wider end of the scale, as roads range from 2.5 to 3 metres, but a consistent measurement for game purposes is better advisable.
Each lane is intended for one vehicle only. In Traveller terms, at the 1.5 metre scale, vehicles travelling on the roads are positioned in the immediate centre of the two 1.5-metre tiles that make up the lane.
A lane includes no "shoulder"; it has no additional road surface to either side of the intended travel zone. Lanes are assumed to have been built right up to the adjoining structures or terrain, and there is no room for a vehicle to pull off to one side in either direction. A lane, by itself, is thus simply a flat surface of pavement 3.0 metres wide and nothing else.
Street
A street is one or more lanes intended to provide access both to vehicles and to people on foot. Vehicles are segregated from the persons using the same street by means of a depressed lane distinct from a pair of relatively-elevated "sidewalks", constructions which are made of concrete, brick, or other similarly durable surface. Sidewalks are 10 centimetres higher than the road surface to produce a "curb" that is intended to force a vehicle to bounce off of the sidewalk and back onto its lanes to reduce or eliminate the likelihood of a vehicle striking a pedestrian who has not stepped onto the vehicle lanes. It is generally considered preferable to cause a vehicle to strike another vehicle than to allow a vehicle to strike an unprotected person.
Sidewalks on streets are approximately 1.5 metres wide, sufficient room for a small adult human woman to lie down or for two people to walk past one another without being forced to dodge one another.
A two-lane street with sidewalks is thus 9.0 metres wide, with 6.0 metres' width of pavement and 3.0 metres' width of sidewalk surface.
Narrow road
A narrow road is a rural road consisting of one or more lanes (almost always at least two lanes) which is not intended to allow pedestrians to walk along its length. Instead of sidewalks, it is buffered on either side by additional road surface, known as the "shoulder". The shoulder provides room for a vehicle to pull off of the road or to have room to swerve around oncoming vehicles that are out of their proper lane positions. On a narrow road, the paved shoulder—or "hard shoulder"—is quite narrow, approximately 1.5 metres in width; another 1.5 metres of fill material is gravel or dirt—or "soft shoulder".
Because a vehicle cannot pull off of the road (with one half on the paved shoulder and one half on the gravel shoulder) without decreasing at least to its off-road speed, there exists the potential of a rear-end collision while a vehicle attempts to slow significantly enough to do so. A vehicle which pulls onto the soft shoulder at road speed must roll against their driving skill to avoid losing control, potentially resulting in a collision or a rollover.
A two-lane narrow road is consists of 9.0 metres' width of pavement, with 6.0 metres of pavement devoted to two lanes and 3.0 metres of pavement devoted to the hard shoulder. There is an additional 3.0 metres of soft shoulder, meaning that the narrow road requires a 12-metre channel to be graded across the landscape.
Wide road
A wide road should not be assumed to be a large number of lanes; the road has the same number of lanes as does a narrow road. The "wide" moniker refers instead to the width of the paved "hard" shoulders, which unlike a narrow road are a full 3.0 metres wide on either side instead of 1.5 metres wide. The road still has 1.5-metre soft shoulders in addition.
Wide shoulders allow a vehicle to swerve around oncoming obstacles at normal speed, preventing the danger of losing control when driving onto the soft shoulder. They also allow a vehicle to pull onto the shoulder at full speed before decelerating, reducing the odds of suffering a rear-end collision while attempting to do so. On high-traffic roads, wide shoulders are proven to reduce the likelihood of vehicle-to-vehicle collisions a significant amount.
A second benefit of the wider shoulders is the additional lateral structural support that the wide shoulder provides to the road surface, increasing the road's longevity. For a nominal initial increase in the outlay cost of the road, the road is capable of handling a significantly larger amount of daily traffic within its expected lifetime.
A two-lane wide road consists of 6.0 metres of lanes, 6.0 metres of hard shoulder, and 3.0 metres of soft shoulder, thus being 15.0 metres wide in total, with 12 metres of paved road surface.
Pad
A pad is a wide surface of pavement intended to provide a wide space for aircraft and ground vehicles to remain parked, or to provide room for a spaceship or starship to land. Pads are not constrained to any particular measurements, although they are typically built in multiples of 1.5 metres in length and width. 1.5 metres can be divided into halves, thirds, quarters, fifths, or sixths without resulting in irrational numbers, so exact measurements can be made easily when constructing unusually-shaped pads.
Road surface
Roads in Traveller at Pre-Stellar technology or above are intended both for the comfort of their occupants and for the protection of the "subgrade", the material which provides the path of the road and prevents the road from slumping or deteriorating due to weather and vehicle load. This is accomplished through the use of "pavement", a typically plastic-like surface which is laid on top of the subgrade. Pavement is best if it is flexible under extreme loads, although to an average human the road surface feels very hard.
The pavement material is typically bituminous concrete or pure concrete, although various other materials can be used, such as tarmacadam (a crushed stone/tar/bitumen mixture). Sometimes the road is left unpaved for economic reasons and simply consists of packed sand or gravel.
At higher technology levels, the road can be paved with more advanced materials, including carbon buckytubes to provide a flexible road surface that can almost never suffer from shear fatigue. Of course, such surfaces come with a commensurate cost increase, and as the amount of wheeled traffic goes down due to improvements in gravity-based vehicles such enhancements become less and less necessary. However, landing pads and other surfaces do suffer from repeated use and still require reinforcement to ensure they remain durable in the long term.
Primitive-era roads: Dirt road
Roads are usually first founded by the native wildlife of a given region. Animals instinctively find the path of least resistance—not necessarily the shortest route—in order to arrive at their destination for the most efficient expenditure of energy. When a given region has varying elevations and terrain features which reduce or eliminate the ability to travel in a straight line, several animals will likely find the same path to be the most efficient to travel to a given destination. Eventually, the animals' repeated movements will trample the terrain and expose the base material of the environment.
Humans and intelligent lifeforms will also recognise these natural paths as the most efficient routes through a given area, and will begin to travel and herd their animals along the same paths. The paths, covered with the scent of humans, will cease to be used by wildlife due to their instinctive fear of predation and the unknown, further increasing the safety of the route.
However, in spite of their effectiveness, the roads are still unsuitable for anything other than periodic travel on foot, due to a number of shortcomings including narrowness, lack of weather resistance, encroachment of foliage and wildlife, lack of a perfectly smooth surface, and the occasional boulder or obstacle around which the path simply splits and rejoins.
Agricultural-era: Governed road
Upon the rise to sapience, most intelligent beings will recognise the importance of being able to reduce the times required to transport their commodities. This entails the manufacture of vehicles such as wagons, barrows, and handcarts.
Natural paths are disadvantageous to vehicles for a number of reasons. The first is the possibility of overgrowth if a road is unused for a significant length of time. A vehicle could find itself unable to travel along a path a tree falls across it, and would have to be unloaded, lifted over the offending obstacle, and then loaded again in order to circumvent the obstacle unless the road was kept clear. The second is the possibility of severe weather causing erosion or elimination of the road surface, leaving a once-usable path terminating abruptly at a dangerously-loose channel of detritus.
Agricultural-era roads involve slashing or burning the encroaching vegetation on either side of the roadway until a path wide enough for people and their herd animals is made and maintained, and trampling the base material of the environment to pack it down to make that path safe for repeated use. Though the road will eventually deteriorate over time due to use, its deterioration due to weather and overgrowth will be reduced or eliminated. A periodic campaign to eliminate encroaching vegetation and to ensure the road remains solid are all that is required to maintain the road in this way.
Early-Imperial-era: Gravel
As technology and population increase, roads see more significant use and require better forms of maintenance in order to be kept. The presence of obstacles such as small boulders and tree roots frequently results in the breakage of domesticated animals' limbs or the destruction of wheels and axles, requiring some sort of buffer between the base terrain and the surface that road users travel upon.
The next technological advancement in road construction is the invention of the "subgrade", a porous and comparatively soft material intended to be laid over top of the base terrain in order to provide a long-term road surface which can be repaired relatively easily. This is known simply as a "gravel road".
Crushed stone from a quarry or naturally-polished stones from a river bed are distributed evenly across the area and are packed down. This provides drainage to the surface, further reducing damage due to weather, and also provides an even, relatively-smooth surface which is comfortable to walk upon and relatively safe for vehicles.
Such roads suffer from compression when wagons are driven over them over time, requiring yearly maintenance to replace the gravel base. This periodic maintenance was itself expensive, as people would be required to inspect the roads and then to rebuild sections of the road on a frequent basis, as often as once per month in high-traffic areas. Engineers had to resort to other solutions to keep the road lasting a long time by reducing the damage that its users would inflict upon it.
Late-Imperial-era: Cobblestone
The invention of pavers to be installed onto the subgrade was the next significant invention. Pavers are small, hard objects which, when interlocked and laid onto a surface, increase the durability of that surface several fold and also serve to make that surface firmer and smoother.
Stones called cobblestones would be carefully cut and interlocked into one of many patterns. These stones, embedded onto the subgrade with the holes filled in with sand, provided an extremely durable—albeit rather hard—surface which reduced the amount of maintenance the road required to a near minimum.
Although the use of brick pavers and cement pavers helped reduce the bumpiness of the roads to a significant extent, the roads were still rather unpleasant at high speed. Users were limited to approximately 25 km/h before discomfort would be felt.
Industrial-era: Surface-treated macadam
The invention of the self-powered vehicle allowed for considerably higher speeds, but the roads were not up to the task. As vehicles began becoming more and more powerful, with top speeds reaching 100 km/h, roads that were previously comfortable to walk on or to drive wagons across at low speeds were found to be extremely uncomfortable at higher speeds. Smoother road surfaces became the order of business.
The idea of using pre-formed cement bricks to make a road surface was adopted well by mainstream society, but the bricks were labour-intensive and still bumpy to drive across. A smoother road surface could be obtained by laying several different layers of stone aggregate across one another on top of the subgrade, with the gravel being compressed through the use of steam and extreme pressure. This road surface was known as "macadam". Vehicles could travel at speeds up to 40 km/h in complete comfort across a macadam surface.
Pure macadam road surface was notorious for dust. To mitigate this shortcoming, once the road had been compressed, a final layer of tar was spread across the surface and allowed to dry. This smoothed out the ride further, protected the macadam surface, and reduced the amount of dust that could escape. Speeds of up to 50 km/h at no discomfort were feasible. When higher speeds became desirable, however, further research was required.
Technological-era: Concrete pavement
The idea of mixing an aggregate material into the cement to produce a thick substance called concrete provided a much smoother surface than cobblestone as there was a pronounced lack of bumps in the surface. With the widespread adoption of rubber tires to mitigate the road's innate tooth and provide traction, the roads became considerably smoother, and the invention of suspension systems further improved the comfort of the ride, allowing ground speeds in excess of 100 km/h to become feasible.
However, concrete is extremely strong, hard, and inflexible, and is also slightly porous to water. When concrete is subjected to extremely heavy loads, it doesn't flex enough to avoid cracking. It is also subject to frost damage in regions with cold winters and warm summers. Although the road lasts a very long time, it deteriorates faster than does a surface-treated macadam road, requiring frequent patching and replacement. A replacement that lasted longer was inevitable.
Pre-Stellar-era: Asphalt pavement
The derivation of tarmacadam—a full mixture of tar and aggregate—from the original concept of macadam covered with tar was the breakthrough needed to provide a smooth road surface that was not only comfortable to drive across and relatively affordable to patch, but also durable and flexible. Tarmacadam road technology lasted a relatively short time and was soon replaced by bituminous concrete, or asphalt concrete, which removed the tar in the mixture and replaced it with pure bitumen (asphalt).
Asphalt concrete is laid out in giant strips like extremely thick paint from a complicated machine known as a "free-floating screed". The asphalt concrete dries into a firm road surface that is very comfortable even at exorbitant land speed in excess of 150 km/h.
Roads made from bitumen and aggregate could last an extremely long time, up to 40 years, before requiring replacement. Additional benefits were the extremely smooth ride, the relative lack of porosity of the surface to prevent frost-shatter, and the recyclability: in-place reheating and remixing of the asphalt concrete allows an asphalt road to be rejuvenated and relaid with little additional material required.
A disadvantage compared to regular concrete, however, was the increased road noise that the surface produced.
Average-Stellar-era: Buckytube pavement
The buckytube road is not actually a road built entirely out of carbon nanotubes, as such a road would be expensive beyond all reason. However, it makes use of individual carbon nanotube fibres built into an interlocking horizontal-tending mesh within the binding material of the asphalt concrete surface through the use of gravitic harmonics—the same technology used to give Tornadium-D its horizontal shockwave. This mesh is incredibly durable and resistant to cracking due to strain, yet still allows the surface to bend and flex with loads.
The durability of the surface is increased by an order of magnitude, at a cost increase of several fold. For passenger vehicles, there is simply no reason to resort to such an expensive road surface unless the cost of acquiring construction equipment is astronomical enough that road replacement after 40 years is economically unfeasible. However, in extreme-traffic areas or in areas subject to starships and other extremely massive objects, a buckytube pavement surface is the clear winner.
Road construction
Planning
Before the road construction process can begin, the road route should be carefully planned. The best road is the road whose costs meet demand and which requires the least amount of fuel to travel along its length. Actual expediency of the route, though somewhat related to these factors, is a side effect at best and is not usually a principal design goal.
The cost of hiring an engineer-architect to plan the path of the road is negotiated on a contract basis. The base price of a contract with an engineer-architect is equal to 1 000 Cr per kilometre of road to plan. Planning the road oneself reduces the operating expenses to 500 Cr per kilometre.
Every kilometre of a road must be individually planned, with the various steps required to make a workable road surface identified. The various characteristics of the terrain and environment serve to determine the difficulty of planning that section.
Terrain characteristics DM Examples ------------------------------ ---- --------------------------------------------- Entirely flat +2 Nebraskan corn fields Flat, small hills +1 Waterloo Gentle, rolling terrain +0 Ohio plains Rolling terrain, some cliffs -1 British Columbia Thompson-Okanagan Broken terrain -2 Albertan Badlands Shallow mountainous terrain -3 Central South Dakota Steep mountainous terrain -4 Colorado Rockies
Environment characteristics DM Examples ------------------------------ ---- --------------------------------------------- Clear +2 Mercurian plains Rare obstacle +1 Lunar plains Uncommon obstacle +0 Martian plains Occasional obstacle -1 European heathland, rural farmland Common obstacle -2 European scrubland, rural village Frequent obstacles -3 Deciduous forest, urban town Thick obstacles -4 Amazon rainforest, urban city
Road width DM Examples Law level DM
-------------- ---- -------------------------- ------------ ----
3.0 metres +2 Single-lane alleyway 0-5 +2
6.0 metres +1 Single-lane narrow road 6-8 +1
9.0 metres +0 Two-lane narrow road 9-A +0
12.0 metres -1 Two-lane wide road B-C -1
15.0 metres -2 Four-lane narrow road D -2
18.0 metres -3 Four-lane wide road E -3
21.0 metres -4 Six-lane narrow road F -4
etc.
The referee may rule that certain side quests, licensing, public works, bribes, and the like may allow the legal DM to be modified positively (beneficially).
| To plan 1 kilometre of a roadway: |
| Routine, Int, Engineering, Admin or Legal or Liaison, 1 hour (safe) |
Referee: Ignore Mishaps, and treat fumbles as simple failures. Apply all DMs and ignore the ±8 DM limit.
|
If there are repeated failures and Determination does not hold out, then the road has reached intractable opposition from the local population or special interest groups, or has reached a technical impasse, and this section of road cannot be completed at all. A different road type may still prove feasible in this section (e.g., an elevated causeway, a tunnel, or a transfer to another transportation medium).
It is entirely possible to plan a road through several hundred kilometres and discover that just one section of the road proves impossible to construct, rendering the entire planned road moot. The engineer-architect will of course still be well-paid for his services...
Grading
The next phase of construction involves engineering a flat surface at least as wide as the road. The difficulty in determining the ability to conduct this grading is part of the planning phase—well in advance of any construction equipment moving into the area, the engineer-architect has already determined the ideal road route and figured a certain amount of grading required. However, after all planning is complete, the work must begin... and as anyone knows, nothing goes according to plan!
Grading consists of three stages: clearing, levelling, and smoothing. For governed roads, clearing is the only process necessary. For more advanced roads, the additional stages are also involved. Any road beyond a gravel road also requires surfacing, as described in the next section.
Clearing is the process of removing obstacles along the road route. This requires lumberjacking services in foliated areas, and demolition services in urban or rocky environments (assuming of course the property for the road route has also been purchased—it may be frowned upon to demolish people's homes without prior approval). Clearing is the road-following axis of grading and ensures that the road is drivable with the number of turns carefully balanced with the efficiency of the road. An improperly-cleared road will require a large number of turns and may result in a greater number of corner-related collisions.
Levelling is the process of alternately carving terrain and filling terrain to produce a reasonable road bed. Levelling involves the side-to-side axis of grading and ensures that the road surface sheds unwanted materials while not forcing drivers to lean unnecessarily. An improperly-levelled road will cause pooling of precipitation or cause road-shoulder-related collisions (such as running off the road or hitting parked vehicles).
Smoothing is the process of adjusting the high points and low points along the road route in order to reduce the number of lands and hills on the route. This allows the road to be more economic as it reduces the need to apply additional acceleration or deceleration, both of which require expenditure of energy and thus fuel. Improperly-smoothed roads will be "wavy" and uneconomic, and may result in a higher number of speed-related collisions.
Clearing process
Clearing involves eliminating obstacles through the use of lumberjacking, demolition, or other removal services. A primitive although not-entirely-ridiculous method of clearing is to use starship weapons or anti-vehicle weaponry to (rather literally) carve a path through the terrain.
On rocky worlds, the immediate path of the road must be cleared. Each individual obstacle must be demolished by manual labour or explosives. The wider the road, the more obstacles must be cleared.
On foliated worlds, the road's immediate path must not only be cleared but all large floral objects (e.g., trees) within a buffer of 6.0 metres of the road must also be cleared. This reduces the ability for natural plant reproduction to cause additional trees to sprout close enough to the road, diminishing the odds that a tree's roots will lift and damage the concrete.
On worlds with native fauna, the road's path must also be guarded somehow against the incursions of animals, as these animals will cause great risk to road users. Usually, this means installing a fence at the same 6.0 metre buffer line. The degree of the fence depends on the size of lifeforms expected in the area. Light ruminants can be deterred by a simple 1-metre wooden barrier, while large pachiderms or dinos may need an electrified fence a storey or two in height.
Note that only the actual path of the road is levelled and smoothed. The cleared area is a fair bit wider than the road's normal width and is used to reduce the danger of running off the road and/or the danger of nearby objects falling onto the road.
TODO
Levelling/smoothing process
In general, grading always requires more material than it removes. The ideal road surface is raised above the terrain slightly to aid in shedding precipitation and accumulation. This can be as little as a dozen tonnes of rock crush and sand for a road across flat terrain, up to several kilotonnes of added material for a road in broken badlands.
Roll 2d6-2 and subtract the Terrain Characteristic DM, Road Width DM, and Environment Characteristic DM from the roll. This is the exponent of the number of tonnes of additional material required for this kilometre of road section, applied to a base of 2. For instance, if the result is 12, then the number of tonnes of material required is {2**12} 4 096 tonnes.
Example: Bartley is building a two-lane narrow road through broken terrain on an airless moon. The Terrain Characteristic is -2, but the Environment Characteristic is +1, for a net DM of -1; the Road Width of 9.0 metres provides no DM. Bartley rolls 2d6-2 and achieves a roll of 6. The DM of -1 is subtracted, resulting in a roll of {6 - (-1)} 7. This section of road requires {2**7} 128 tonnes of added material.
In addition to added material, the terrain also requires existing material to be adjusted. For the amount of material that must be excavated from the road route and then repurposed somewhere else along the road route, again roll 2d6-2 and subtract the Terrain Characteristic DM, Road Width DM, and Environment Characteristic DM. Apply the resulting figure as an exponent to a base of 2.5. For instance, if the resulting roll is 8, then the road manufacturers must excavate {2.5**8} 1 525.8 tonnes of material along the given kilometre of road, which is then redistributed in the same area it was extracted.
Excavated material does not require a significant amount of shipping and is thus more economic than added material, but also requires more effort to achieve the same benefit.
Additional material/workmanship
Voluntary addition of extra material or increased excavation and redistribution increases the smoothness or levelness of the road surface. For each doubling of either added material or reworked local material, the quality of the road surface increases by +1 (see "Completion"). The maximum modification is +2 from extra material and +3 from increased excavation.
Surfacing
TODO
Completion
TODO
Road upgrading
TODO
