What ever happened to monorails?

which seemed like another good idea at the time.

Introduction

On paper, at least, monorails have a lot going for them. Monorail trains are grade-separated, because they run on overhead tracks, so they are fast and safe. This is a major improvement over trains and buses, and without having to run subway trains underground, which is expensive - and why should pedestrian go underground, out of the light, and without a view?

The biggest obstacle to monorails is cost. Monorails cost about twice the cost of a comparable light rail system. Light rail costs £20-30m/km in the UK, and a monorail would cost in the region of £40-60m/km.

Cost

The obvious question is - why should monorails cost more than light rail? The easy answer is that, as a rule of thumb, elevating a structure doubles its cost. This is less than convincing for monorails however, when they are compared to light rail. They are, after all, different transport technologies.

Installing light rail is a complex business. Firstly, the whole road must be torn up, in order that the utilities underneath the road are found, and moved out of the way of the tracks - once the track has been laid, it cannot be removed in order to provide access to the utilities. The road surface must then be relaid, and then dug up again in order to install the foundations of the tracks.

By contrast, the tracks for monorails are pre-fabricated off-side, and are then bolted together in situ. This makes building a monorail track easy and fast. So monorails should cost less than light rail.

A more convincing reason is as follows. Light rail systems are designed with a standard gauge. It provides greater choice in the vehicles that can be bought, at that time and in the future. By contrast, as can be seen in Figure 1, monorail beams, around which the undercarriage is wrapped, vary greatly from one system to the next. The width of the beam is more important than the height, since the undercarriage doesn't wrap around the bottom of the beam. The location of the power supply rails of either side is, however, very important, as this restricts the trains that can run on the track.The consequence is that each monorail system is turnkey, and the contracts are inflated accordingly. Ultimately, this damages the interests of the monorail companies, as they sell very few systems every year. A vicious circle is set up, of increased costs, and few sales.


Figure 1: Monorail beam cross-sections

Visual Blight

One issue comes up regularly with monorails, and that is the question of visual blight from the concrete rail and the concrete support pillars. However, there are other pieces of infrastructure which are far more brutal. Figures 2 through 4 show the GWR railway line as it enters Bath Spa railway station. Due to the topography of Bath by this point the railway line is elevated by approximately 4m, on a dark brickwork viaduct, whereas the typical building colour is light stone.


Figures 2-4: GWR rail viaduct, Bath

Part of the reason why the viaduct fits into Bath is that it is hidden to an extent by foliage, and because it runs behind the garage and other office buildings and houses. Part of the reason is that the viaduct has been in Bath for a long time (the GWR was built by IK Brunel in 1836), and so people have got used to it.

By comparison, a monorail line in Sydney, Australia,is shown in Figure 5. The visual blight of the monorail system is clearly less than that of the GWR in Bath.


Figure 5: Sydney Monorail (WM/ Greg O'Beirne)

More information on the visual impact of monorails can be seen on the Monorail Society web-site.

What Next?

The cross-section data for Figure 1 was taken from Considering Monorail Rapid Transit for North American Cities by Ryan Kennedy (undated). The same document gives a hint at a possible resolution:

"Many of the Series 1000 monorail’s new features became the standard adopted by the Japanese ministry of transport in conjunction with the Japanese monorail association in a push to lower costs through standardization."

Standardisation would require the setting of standards for the following quantities:

The capacity of the power supply in amps is dependent on the power generation, which is separate to the track, and which could be upgraded as required.

Metrail supplies monorail systems with an internal hybrid drive system. Under the process of standardisation, however, any train units supplied would have to run on the standardised beam, and make allowance for the presence of the power supply rails.