Cuts , fills, tunnels or bridges?

JonMyrlennBailey

Well-known member
When building a railroad track or a motor road, one might come to a high spot of terrain that gets in the way.

There are a number of options:

1. build the road around the high spot
2. bore a tunnel through it
3. cut through it


When building a railroad track or a motor road, one might come to a low spot of terrain or a body of water that gets in the way.

There are a number of options:

1. build the road around such low spot or body of water
2. build the road over a dam or along a levee
3. build a trestle, causeway or bridge
4. fill the low spot or body of water with mother earth


So, what are the factors that determine how road builders negotiate such natural obstacles that get in the way?

1. Cost
2. Convenience
3. Laws and Regulations
4. Efficiency of Finished Road
5. Safety Considerations
6. Travel Time Saved by Choosing One Option over Another
7. Other Factors
 
It's usually the cost. Everything for railroads and roads is how much it costs and they choose the easiest and least expensive way to get between wo points. Railroads need to be as flat as possible and will use long sweeping curves to avoid steep grades by going around them if they can. If the obstacle is impossible to avoid, then they'll cave in and build a tunnel. Tunnels are the costliest and the most time-consuming part of the construction process. Sometimes, there is no way to avoid a grade and a grade is built with the minimal amount of grade as possible. Again, the line will be built using sweeping curves, narrow gauge being an exception, to allow for easier climbing and descent on the route.

There are old books, freely available by the way, from Google's Gutenberg Project and from www.archive.org on this subject. These were engineering textbooks from the beginning of the last century on railroad surveying and building. They're pretty interesting, and yes there's a lot of math in there too.
 
It's usually the cost. Everything for railroads and roads is how much it costs and they choose the easiest and least expensive way to get between wo points. Railroads need to be as flat as possible and will use long sweeping curves to avoid steep grades by going around them if they can. If the obstacle is impossible to avoid, then they'll cave in and build a tunnel. Tunnels are the costliest and the most time-consuming part of the construction process. Sometimes, there is no way to avoid a grade and a grade is built with the minimal amount of grade as possible. Again, the line will be built using sweeping curves, narrow gauge being an exception, to allow for easier climbing and descent on the route.

There are old books, freely available by the way, from Google's Gutenberg Project and from www.archive.org on this subject. These were engineering textbooks from the beginning of the last century on railroad surveying and building. They're pretty interesting, and yes there's a lot of math in there too.

It might be cheaper for building automobile highways mile per mile than standard gauge rail lines. Motor vehicles can tolerate sharper curves and more extreme grades especially on pavement. Cars can brake and accelerate much quicker than trains to boot. Mile per mile, is it really more expensive to erect a bridge vs bore a tunnel? Won't a bridge be more costly to upkeep in the long run than a tunnel?
 
It might be cheaper for building automobile highways mile per mile than standard gauge rail lines. Motor vehicles can tolerate sharper curves and more extreme grades especially on pavement. Cars can brake and accelerate much quicker than trains to boot. Mile per mile, is it really more expensive to erect a bridge vs bore a tunnel? Won't a bridge be more costly to upkeep in the long run than a tunnel?
Sure. Roads are easier to build. A tunnel vs a bridge? A tunnel is used to pass through or go under an obstacle. I will assume that bridges are generally more expensive in the long run due to their structure maintenance but are less expensive than a tunnel to build.
 
So, what are the factors that determine how road builders negotiate such natural obstacles that get in the way?

1. Cost
2. Convenience
3. Laws and Regulations
4. Efficiency of Finished Road
5. Safety Considerations
6. Travel Time Saved by Choosing One Option over Another
7. Other Factors
A retired US Engineer's thoughts:
The location and design of roads and rails is an iterative process done in phases. The planning phase involves developing several alternative alignments including a do nothing alternative. The environmental and social impacts, construction costs and constructability of each are identified and compared. Economic analysis is also performed to help determine the most cost effective solution, e.g., go around it, through it or over it. The best components of each alignment alternative that minimize impacts, minimize cost and have desirable constructability are merge into a final alignment alternative. The final alignment is taken into the design phase which includes both preliminary design and final design. Final design plans are used for construction. Public roads are planned and designed to meet demand 20 years in the future. The demand volume 20 years in the future determines the number of lanes. New rail location and design projects are rare. Existing track alignments and right-of-way are almost always used so the planning phase is skipped. Private railroads are profit oriented and therefore planned improvements are for a much shorter timeframe. I am told railroad business plans rarely go beyond 5 years. An economic cost-benefit analysis is performed that includes construction costs, operating costs, vs revenue benefits and time savings benefits. When the benefits are greater than the costs a single track gets more sidings or a single track with sidings gets double tracked. Safety is the primary reason for converting at-grade crossings to grade separated crossings.

1. Cost: Cost is the primary decision factor for roads and rails. Environmental regulations may require a more costly design to avoid an environmental impact. Costs for construction, right-of-way, earth work, bridges and material costs i.e. concrete vs steel vs timber as well as maintenance costs are all taken into account. In urban areas there is also consideration given to road bridge aesthetics. Some times a 'signature' bridge which has a higher cost is acceptable to make it a unique landmark.
2. Convenience: Not sure what you mean by convenience?
3. Laws and Regulations: Environmental regulations and design standards dictate road and rail design for the desired design speed. Horizontal and vertical curves and grades as mentioned above are different for different types of roads, two-lane two-way local roads vs 2-lane oneway freeways and rail. Design speed dictates minimum horizontal and vertical curves and super elevation. For roads stopping horizontal and vertical sight distance is also a factor. If there is an object on the road a driver needs to be able to see it in time to stop. I am sure you are familiar rail design maximum grades, curves and superelevation. At higher speeds railroads use spiral curves between tangent track and curved track sections to ease the rolling stock into and out of the curve. Roadways do not use spiral curves but do have minimum tangent sections between curves, and reverse curves are a no no. for driver safety.
4. Efficiency of Finished Road or Rail: As you said above the shortest distance between two points is a straight line and building something as straight and as flat as the design standards allow yields the lowest construction costs and also the lowest operating costs. Economic analysis of alternatives is common practice.
5. Safety Considerations: Covered by #3 and #4
6. Travel time: Not directly considered in new highway or new rail designs but is considered for certain types of highway improvements. Travel time or rather delay is considered in the rail decision to double track.
7. Other factors: You covered them all pretty well.

Terrain options:
In rolling terrain the alignment is usually straight or slightly curved to balanced cuts and fills to lower construction costs.
In mountainous terrain a curved alignment follows the elevation of the mountain topography along the valley. If that is impractical to get to the other side of the mountain a tunnel is bored. Bridges are built to span a valley when the alignment goes between mountains.

Natural obstacles:
The decision to bridge a river or tunneling under it, go around the mountain or through it, go over a lake or around it depend a lot on the alignment and the type, size, elevation or grade change, location of the obstacle, and the cost of alternatives.

Gosh I really didn't mean to write a thesis on this. Can you tell I miss my work?
 
Gosh I really didn't mean to write a thesis on this. Can you tell I miss my work?
Nah not at all!

Thank you for the inside view into the complexity of real-life route building. We really don't appreciate the hard work that goes into the process of route design and building when all we need to do is lay our track and place our roads hell be damned to any obstacles, NIMBYs, or the environment.

We can sort of get close to the process by building a route on a prototypically generated terrain. I've taken TransDEM generated terrain and laid down track where no railroad was ever located. Surveying the route around hills, over rivers, and existing infrastructure is not an easy task and makes the route-building process more challenging.
 
I thought of convenience in terms of being a MOTORIST. Naturally, I want to avoid traffic jams and delays if at all possible. Sometimes extra highways are constructed to reduce travel time between two cities or such. They are called connectors. It might be more convenient (and certainly more cost effective) to route a new road over an existing dam than build a new separate bridge. True or false?

You have to think of the benefits and shortcomings to the ROAD USERS of the finished product (including private automobile drivers) as well as the road builders.

How often are roads built and maintained for YOUR benefits as a car driver?

It's true in America that new railroad right-of-ways are rarely founded except maybe in new theme parks. Over the past 100 years, 55% (over half) of our nation's collective railroad track has become defunct or abandoned by railroads. Much of RR right of way has been converted in rails-to-trails projects. It's a shame. Modern culture doesn't appreciate trains much anymore. There are national high-speed trains on the horizon, however. The world's most advanced ones now are in Europe and Japan. This might be necessary to open up more new RR right of way in North America. Tracks laid by slaves with hammers in the 1800's won't cut it for 21st century 300-MPH bullet trains.

North America seems to lag in infrastructure and ground transportation advancement though America can lay claim to putting men on the moon, creating and fielding the first nuclear weapons and inventing the airplane.
 
Last edited:
Nah not at all!

Thank you for the inside view into the complexity of real-life route building. We really don't appreciate the hard work that goes into the process of route design and building when all we need to do is lay our track and place our roads hell be damned to any obstacles, NIMBYs, or the environment.

We can sort of get close to the process by building a route on a prototypically generated terrain. I've taken TransDEM generated terrain and laid down track where no railroad was ever located. Surveying the route around hills, over rivers, and existing infrastructure is not an easy task and makes the route-building process more challenging.
I don't have the imagination needed to build a route from scratch. I need to follow a model train plan or use Transdem to create a prototypical route. I've been using Lidar DEMs in TransDem with Traniz which gives an accurate interpretation of topography, but as you know the but the ground elevation precision is off a bit with 10m grid but better with the 5m grid. Certainly good enough for Trainz. I think the classic surveyor's smooth spline tool does a good job of automatically performing cuts and fills in terrain. I've learned that you can apply the tool more than once to the same spline and get a slightly different cut/fill terrain look.
 
I don't have the imagination needed to build a route from scratch. I need to follow a model train plan or use Transdem to create a prototypical route. I've been using Lidar DEMs in TransDem with Traniz which gives an accurate interpretation of topography, but as you know the but the ground elevation precision is off a bit with 10m grid but better with the 5m grid. Certainly good enough for Trainz. I think the classic surveyor's smooth spline tool does a good job of automatically performing cuts and fills in terrain. I've learned that you can apply the tool more than once to the same spline and get a slightly different cut/fill terrain look.
Hand-sculpting terrain is hard to get right. I use that sparingly now myself and also prefer real-data or use displacement maps. In the olden days, this was all we had and I was always amazed at what people accomplished.

Some time ago, I placed an interurban line along a roadway that runs both freight and passengers. This area doesn't have any rail service and never had considering it was an exclusively an uber-wealthy area located on Eastern Point near Gloucester. Putting in the line had the following rules applied:

The route had to be plausible.

The terrain could be modified as needed but kept as close to the original as possible.

The railroad had to impact the current roads as minimally as possible, taking into consideration crossings and other existing infrastructure.

In the end, the route climbed up and over a minimal grade and ran parallel to an existing road with numerous crossings for the side streets. When viewing the operation, it appears this was that really existed.

The cuts and grades created by smoothing the terrain under the spline do work well. As always, I lock the tracks to preserve their grade and height and I find that for level parts, using the terrain brush works well for smoothing the terrain because I can control the width of the ROW. Those areas where there are grades, however, work better with the smooth spline tool.

Yes, we're stuck with lower resolution terrain compared to the real world, but that's the breaks we need to consider due to our hardware limitations. HD Terrain comes a long way towards the smoother and more accurate terrain, but there are still huge limitations with that including file sizes.

I have found that with the 5 m grid, the heights are pretty accurate when measuring the terrain and comparing to ground height in the same location on Google Earth. I've used this method on a prototype project. Where bridges and other manmade objects have caused the terrain to rise up on the DEM-data, I've been able to reinterpret the actual height of the ROW below. This required manually gathering the height on Google Earth and entering in the height on the track height tool before smoothing terrain underneath or using the same measurements for manual terrain smoothing.

On another project I've been working on, I had to literally dig out a river bed from an existing reservoir. I used old topographic maps for the height measurements and then dug the terrain down to the height where the riverbed once existed. There was a lot of artistic licensing here but the results were amazingly accurate. The measurements were surprisingly accurate considering we have steps to deal with in the digital world.

We do run into other limitations though such as bridge abutments and river crossings where the resolution is too low to build a proper embankment or grade no matter we try. It's locations like this that require a compromise and a lot of times embankment splines to fill in the gaps.
 
Reality shows that trenches and slopes predominate on railway lines, the tunnel as a last resort when it is not possible to adopt the previous ones.
 
I thought of convenience in terms of being a MOTORIST. Naturally, I want to avoid traffic jams and delays if at all possible. Sometimes extra highways are constructed to reduce travel time between two cities or such. They are called connectors. It might be more convenient (and certainly more cost effective) to route a new road over an existing dam than build a new separate bridge. True or false?

You have to think of the benefits and shortcomings to the ROAD USERS of the finished product (including private automobile drivers) as well as the road builders.

How often are roads built and maintained for YOUR benefits as a car driver?

It's true in America that new railroad right-of-ways are rarely founded except maybe in new theme parks. Over the past 100 years, 55% (over half) of our nation's collective railroad track has become defunct or abandoned by railroads. Much of RR right of way has been converted in rails-to-trails projects. It's a shame. Modern culture doesn't appreciate trains much anymore. There are national high-speed trains on the horizon, however. The world's most advanced ones now are in Europe and Japan. This might be necessary to open up more new RR right of way in North America. Tracks laid by slaves with hammers in the 1800's won't cut it for 21st century 300-MPH bullet trains.

North America seems to lag in infrastructure and ground transportation advancement though America can lay claim to putting men on the moon, creating and fielding the first nuclear weapons and inventing the airplane.
Thanks for explaining your thoughts on convenience. The convenience, I think, comes with the decision to connect point A to point B in the first place. User costs are definitely a component of economic analysis of the build decision. Their affect on the decision making depends on the alternatives being considered with a doing nothing alternative. For the most part, existing roads are widened to add lanes to meet capacity demands because its less expensive. The exception would be when cost of right-of-way for taking homes & businesses to widen far exceed the cost to build a bypass around a city or lake rather than go through it.

Roads are public so they are always built and maintained with public money for all users, commercial and non-commercial.

Jon you are so right about 1800 rail alignments not being up to High Speed Rail (HSR) standards. I've participated in a few high speed rail (HSR) projects in the US and the US HSR philosophy to compete directly with short distance air travel ~ 1 to 2 hr flights, using existing RR right-of-way with track upgrades and curve alignment modifications to achieve design speeds under 200mph. In the US HSR speeds will never be anywhere near the 300 mph speeds in Europe or Japan. The US government and the public just not pay for the right-of-way needed to achieve speeds above 200 mph. For example, the Amtrak Acela's top speed of 155mph is for only about a 50 mile segment through out the entire length of the North East Corridor which is 460 miles. The Florida Brightline HSR from Orlando, to Coco, to Miami, Fla will only operate at its top speed of 125 mph on the segment from Orlando to Coco. The segment from Coco to Miami operates on existing FEC track. Brightline West, now under construction from Victorville, Ca to Las Vegas, NV will be built almost entirely within the Interstate 15 right-of-way and located in the median between eastbound and westbound. The promotional info states 'speeds up to 200 mph. Not sure what's going on with the California HSR other than its way overbudget and way behind schedule.
 
Costs, costs, costs.
Not everything is costs in the railway, although from an economic point of view a trench is indeed cheaper than a tunnel.
In life, reality often exceeds the economy and in the railways as well.
In the nineteenth and early twentieth centuries the railway passed through the towns that paid for it, if the next town paid more because it passed through the latter, it was not a question of costs.

Political motives also come into play, in Spain a railway line was built in the nineteenth century that in 20 kms had 17 metal viaducts (I am recreating the same one in Trainz), well, the one who paid for the very expensive construction was the neighboring country, Portugal, because it wanted a much shorter connection with France (Paris). The costs "were not there and were not expected".
In general, when the railways were nationalized (Europe), costs became of the utmost importance.

Anyway, when in Trainz you think that the route you are making is absurd, you can apply what I write.

Regards, Javier
 
Costs, costs, costs.
Not everything is costs in the railway, although from an economic point of view a trench is indeed cheaper than a tunnel.
In life, reality often exceeds the economy and in the railways as well.
In the nineteenth and early twentieth centuries the railway passed through the towns that paid for it, if the next town paid more because it passed through the latter, it was not a question of costs.

Political motives also come into play, in Spain a railway line was built in the nineteenth century that in 20 kms had 17 metal viaducts (I am recreating the same one in Trainz), well, the one who paid for the very expensive construction was the neighboring country, Portugal, because it wanted a much shorter connection with France (Paris). The costs "were not there and were not expected".
In general, when the railways were nationalized (Europe), costs became of the utmost importance.

Anyway, when in Trainz you think that the route you are making is absurd, you can apply what I write.

Regards, Javier
In the early days in the US, cities and towns sponsored the rail lines. The people building the railroad would sell stocks and the various towns would put up a stake in the railroad. The railroads would change names as they reached a new city or town. The Essex and Haverhill connected to the Haverhill and Andover and so on to eventually create what became the Boston and Maine Railroad.

Some of the wealthier towns would sway the railroad their way even if the route wasn't a direct one. In my area, the now long-gone Lawrence and Lowell railroad, basically a branch of the Boston and Maine, built between the namesake cities was swayed to go south first on the way to Lowell via Tewksbury instead of taking their planned and surveyed route along the Merrimack River. This made for a longer journey, not by much, but it did change the route a lot because it meant the company now had to survey across swampy land and over some hills instead of following the relatively flat and straight trip along the river.

In other instances, another railroad will determine the route of another. The Boston and Albany Railroad was at one point the only connection west out of Boston. The Boston and Maine Railroad wanted its own route west. The wealthy paper mill owners in Fitchburg wanted to connect to points west to Troy, NY, and formed the Fitchburg and Troy Railroad for the purpose, but were fought tooth and nail due to the B&A meddling with the state legislature. They did some "influencing" to prevent the building of this line. The railroad also had to stick to a rather awkward route instead of heading south and west where the hills are easier. The biggest obstacle though was the Hoosac Tunnel. The B&A really forced the hand of the governor and state legislators who put on financial restrictions. With money tight, the state took over the tunnel project but kept the money really tight which prevented progress then complained to the engineers that no progress was made! Eventually, the line did open in its entirty 1875 when the tunnel was completed about 30 years after its inception.

Sometimes, a railroad was built to siphon off traffic from a competitor. These lines operated at a loss but were built nonetheless. The Eastern Railroad, an arch competitor of the Boston and Maine Railroad, supported a wholly-owned subsidiary called the Essex Railroad. The line was called that because it existed only in Essex County in Massachusetts. This railroad never made money and was bankrupt very quickly after it opened due to lack of business except on either end, but it was built to take traffic from Lawrence to Peabody and Salem on the Eastern Railroad and away from the Boston and Maine Railroad. Lawrence, like Lowell back in the 1840s was a burgeoning textile center. The city was built in 1842 by the Lawrence brothers from Lowell. They set up a planned city with worker's houses and mills. Other companies followed and the city, like Lowell, became a huge textile manufacturing center.

Eventually, the Eastern Railroad, like the Boston and Lowell Railroad, became part of the Boston and Maine. The merger occurred in the late 1880s. The L&L branch lasted until the 1940s and the Essex Railroad lasted until the 1920s. A portion of the Lawrence and Lowell is still operated in Lawrence to the South Lawrence Industrial Park with the Lowell to Tewksbury portion disappearing in the 1980s. Sadly, none of the Essex railroad survives. Portions were operated until the 1980s on the Lawrence end and the Peabody and Salem end discontinued in the early 2000s after a bridge burned.

This history is almost like playing Railroad Tycoon or Locomotion game against competing railroads.
 
Great description John, thank you. :)
Of course, I have involuntarily internalised the European version of the railway. In the United States, the construction of the railroad was parallel to the construction of a new world, new cities and towns, new roads, etc., etc.

When the railway was "invented", it was based on the Roman "Cursus Publicus"; State transport and mail service of the Roman Empire founded by Emperor Augustus for the transport of couriers, officials and tax revenues between Italy and the provinces. Military roads were used that did not always coincide with the famous Roman "Viae" civilian roads.
Suetonius in "Lives of the Twelve Caesars, Augustus XLIX" said:

"In order to make it possible to announce and make known more quickly and easily what was happening in each province, he had young men placed at short intervals along the military roads, initially young men, and later carriages. The second procedure seemed to be the most practical, since the same men who bring the shipments may also be questioned, if occasion requires."

As on public roads, every 15 or 20 miles refreshment and interchange points called "Stacio" were created and the founders of the railroad wisely maintained the imperial scheme and name on the railroad lines. From "Stacio" derive "Station" in English and "Estación" in Spanish , as well as "Wagon" in English or "Vagón" in Spanish.

I don't bore you anymore, just like John Doe would say.......... It's all invented........ :giggle:;)

Regards, Javier
 
Last edited:
Back
Top