Transportation Deployment Casebook/2024/Monorails

Introduction

Monorails are railways systems where the track used to move the carriage is a single, continuous line. They work similarly to traditional heavy rail or tram systems, transport a carriage across a predetermined track, but can be elevated above existing infrastructure, and take up comparatively less space than the former options, making them better suited for transport across populated areas such as cities. As such, they have a few desirable qualities as a public transport system, as an elevated transport network, they are separate from the road network, which would naturally be taken up by cars and buses, and provide an elevated view of the local area, which is good for tourists visiting the city.

The history of the monorail is hard to correctly classify as the term has been used interchangeably for various different transportation methods. As the name suggests, the term was often used to describe railway systems where only a single main beam was used, historic designs could be related to bicycles balancing on a railway line, whereas modern designs involve a carriage that straddles a double-flanged metal beam for support.

The two most common modern designs differ on where the carriage is in regard to the rail that guides the wheels, either riding above or suspended below. Modern designs are powered by electricity which is obtained from the rail it rides on, although older designs used steam, coal or even horses as power. Monorails are adaptable in their application, ranging from smaller operations such as moving passengers in a theme park or airport, to larger areas which sometimes span smaller cities.

Before the Monorail

Prior to the invention of the monorail, traditional dual railway trains were used in their place. Their initial intention was as a cheaper way to transport cargo across land in newly settled cities, moving resources from ports deeper inland or moving products from mines back to cities or ports for trade. As the monorail naturally required only one beam, they were often considered a cheaper alternative, although potentially less consistent. Another advantage was that compared to traditional, bulkier train carriages, they were slightly easier to build on mountainous terrain as they were thinner and required less space, making them more suitable for the shorter distances transportation of goods along mountainous uncharted terrain as virgin cities looked to expand further inland.

Early Designs and the History of the Monorail

The Cheshunt Railway is commonly cited as the first instance of a passenger-carrying monorail. The design of the carriage was based on the 1821 patent by Henry Robinson Palmer, who theorized a carriage that equally balanced itself on a single elevated rail line. The carriages would hang off either side of the center rail such that the center of gravity was below the rail. For many years monorails designs would be powered by horses, monorails did not use steam engines until 1876 with General Le-Roy Stone’s design in the Philadelphia Centennial.

During the early history of their existence, monorails were not often geared towards moving passengers, however some were still used for passenger transport. A famous example is the Listowel and Ballybunion Railway that ran from the Irish port city of Ballybunion to the inland market town of Listowel. The carriage design was similar to Palmer’s design, where two carriages had to be equally balanced on either side for the system to move. Despite this flaw, it remained successful for many years as it was the only passenger monorail service in the British Isles for most of its service from 1888 to 1924 until it was decommissioned due to increasing service costs and competition from road networks.

The oldest monorail that is still in commission was built in 1901 in Germany by Eugen Langen, the Schwebebahn suspension monorail in the city of Wuppertal. As a suspension railway, it bears some resemblance to the Enos Electric railway demonstrated over a decade prior, however no direct connection has been confirmed. Technological Advancements for the Monorail Up until the early 1900s, the generic design of the monorail did not stray far from Palmer’s original design, which was effectively a balanced bicycle on a singular rail. However, past this point, some started to innovate on the idea, creating the straddle-type monorail, which modern monorails still use today. The straddle-type differs from Palmer’s original design, rather than a single wheel that rode on a rail, instead, there are multiple wheels that all move along an I-shaped beam, effectively “straddling” the center beam, thus greatly improving safety and reliability compared to the original designs.

A third concept for a monorail was created and later patented by Louis Brennan in 1903. A monorail that stayed upright through the use of a gyroscope. While the design was proven to be successful, where even if all the passengers were sat to one side, the carriage was able to remain upright, it was never put past the testing and prototyping stage due to concerns over the requirement of a functioning gyroscope. If it were to ever fail, then the entire carriage and all its passengers would fall over, thus Brennan’s design never got past the testing phase and was never used for actual transportation purposes.

Limitations of the Monorail

Despite their advantages in cost reduction, monorails were not adapted in their early history and even now, they are relatively unpopular when compared to heavy rail or trams. Due to the relative unreliability, workers often resorted back to the classic dual railway systems for longer distances, in fact modern monorail systems do not go beyond 100 kilometers in length, as at that point, conventional rail systems would simply be preferable, as there were often able to go faster due to their stability.

In the modern era, three main issues affect the widespread adoption of the monorail as a primary mode of transport. The main one being cost, as the monorail requires an elevated network to function, it is expensive to build long connections above the road network, massively inflating the cost compared to maintaining an already existing road, or constructing a tramline on the ground. Due to how the monorail is connected, it often requires specialized trackwork separate from existing systems which increases the cost substantially.

The second issue is that of track crossing, the straddle-type monorail that is used in modern cities does not allow for easy ways to change lines, as the carriages must always remain in contact with the rail. Dedicated areas to change lines for monorails is possible, but it is a slow process and can be expensive to construct and maintain.

Finally, the general urban plan for modern Western cities stifles the effectiveness of the monorail. Monorails are often intended for short-distance journeys, riding above the traffic of a road network, however in Western cities, they often plan to expand outwards into suburbs, where a road network or cars would be far more efficient.

Currently, the main areas where monorails are still employed in cross-city transport are in Asian megacities such as Chongqing, China, Mumbai, India and Tokyo, Japan. The reason these cities use monorails is that they are much denser than Western cities and as such, to facilitate a higher population with a much smaller area, they often build vertically, which fits well with the monorail’s need for elevated structures. Therefore, dense megacities are one of the few places around the world where monorails still see regular use, with the larger cities reaching hundreds of thousands of daily riders.

Visualization of Monorail Ridership

Due to the lack of widespread adoption of the monorail as a viable solution, data about its historical ridership and predicted ridership is scarce. The following data uses the yearly ridership statistics of the Kuala Lumpur Monorail from 2004 to 2023 to visualize the growth of the service.

Compares the predicted vs. real annual ridership of the Kuala Lumpur Monorail from 2004 to 2023

Comparing the Predicted vs. True annual riders of the Kuala Lumpur Monorail

Year	Predicted Annual Ridership	True Annual Ridership
2004	13,291,724	10,956,675
2005	14,739,540	14,482,676
2006	16,192,226	17,380,337
2007	17,622,749	20,142,772
2008	19,005,696	21,765,233
2009	20,319,008	21,021,390
2010	21,545,229	22,108,308
2011	22,672,146	24,200,299
2012	23,692,830	24,435,931
2013	24,605,174	25,437,621
2014	25,411,107	24,303,465
2015	26,115,648	25,067,866
2016	26,725,956	24,200,299
2017	27,250,469	16,841,630
2018	27,698,190	12,594,377
2019	28,078,148	12,573,738
2020	28,399,012	7,143,534
2021	28,668,846	4,226,329
2022	28,894,970	11,496,524
2023	29,083,911	18,107,573

Methodology

The approximate life cycle of a technology can be roughly represented by following formula:

S(t) = S_max/[1 + e^{(-b*(t - ti))}]

Where in this scenario:

S(t) = expected annual riders at a given time t

t = time (years)

S_max = an estimated max amount of riders

b = estimated coefficient

t_i = inflection time, approximate time at which half Smax is achieved.

The above graph was achieved using the following estimations:

S_max = 30,000,000

b = 0.194031

t_i = 2005.179

As seen in the above graph and table, for the first few years of the tracked data, the predicted trend was relatively close to the actual ridership, however around 2017, ridership sharply fell, then cratered further in 2019 with the global COVID-19 pandemic.

The drop in ridership in 2017 is not confirmed, however local reporters claim it is due to a spike in fare prices of public transport at the time, and many citizens just used cars and private transport instead. As the pandemic cleared up in late 2022 and 2023, ridership has seen another rise back to normal levels and is getting closer to the estimated trend. Due to the sharp decreases in annual ridership, the graph has not yet reached a maturity point and an inevitable fall, although if no major loss of ridership occurs in the future, this will happen.