vol 8, issue 2

Making tracks: high-tech roads

11 February 2013
By Mark Williamson
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A straight road vanishing into the horizon

A look at the engineering behind the US road network

A long empty road with just a motorcycle travelling along it

The US is defined by its thousands of miles of interstate road networks

Crumbling road

Two-lane interstate highways were authorised in 1921

Route 66

Route 66 ran from Chicago, Illinois, to Los Angeles, California

Few road networks conjure up the romance of those in the US, but what technology lies beneath the asphalt?

In Europe, much of the built environment is historical and difficult to alter, but in the United States, where the historical record is much shorter, the scope for evolution is greater. No part of the built environment illustrates this better than the interstate transport infrastructure. In less than 100 years it has evolved from jalopies and graded roadbeds to electric hybrids and electronic toll collection.

Wherever we live, we tend to take roads for granted... until they are closed by accidents or restricted by roadworks. It is no secret that the US is defined by its road network: viewed from space at night, the nation resembles a classical topological network of nodes and links, formed by the cities and freeways. On closer inspection, the links are, in fact, chains of smaller nodes joined together by the interstate road network.

Building a network

When the first cars powered by internal combustion engines were introduced to America in the 1890s, the nation was faced with a challenge common to other countries in that existing roads were intended for horse-drawn carts and wagons. Thus it was no coincidence that the early 'horseless carriages' were designed with similarly 'ruggedised' suspension systems. But a particular challenge if the nation was to be fully connected was its breadth of 3,000 miles from east coast to west.

It is tempting to think that all American roads of the 19th century were little more than dirt tracks and cart ruts, but in the more developed east the higher density of population demanded better.

One of the best-known names in road building is John McAdam, who was born in Ayr, Scotland, in 1756 and began his experiments with road construction in the 1780s. By 1816, having been appointed surveyor to the Bristol Turnpike Trust, he had developed what later became known as the 'Macadamised System'. In essence, it comprised a 'graded' mix of crushed stone bound with gravel set on a base of larger stones; significantly, its profile exhibited a slight camber – sloped towards the edges – so that rain water would run off rather than penetrate the foundations.

The first such surface in the US was laid on the 'Boonsboro Turnpike Road' – a turnpike being a toll road – between Hagerstown and Boonsboro, Maryland, in around 1823. According to the specification, rocks were broken "so as not to exceed six ounces in weight or to pass a two-inch ring" and the three layers were compacted using a cast-iron roller.

The first attempt to develop a road that would cross the continent was the so-called National Road, or Cumberland Road, which started in Cumberland, Maryland, and headed due west through Pennsylvania, Ohio, Indiana and Illinois. It was intended to reach the Mississippi, but funding from the federal government ran out and construction stopped some 60 miles short in 1838.

Once Henry Ford introduced his popular 'Model T' in 1908 and America became a budding nation of car drivers, there was a growing need for better roads. For one thing, the dust drawn from the road surface by the low pressure created under moving vehicles was a nuisance and exacerbated surface degradation. Initially, this was addressed by spraying tar onto the surface, creating 'tar-bound macadam', but by the 1920s the paving method of choice was to mix asphalt with the aggregates before they were laid, creating what was known in the US as 'blacktop' and elsewhere as 'tarmac'.

Charging technology

Today, the composition of the roadbed is of little concern to motorists, unless it is allowed to deteriorate. They are interested, however, when it comes to charging for the use of the road, and are sometimes troubled by the use of technology in extracting their hard-earned cash.

Arguably the simplest charging model is to slap a tax on fuel. According to Robin Lindsey of the University of Alberta's economics department: "User-based road transport taxes were pioneered by the state of Oregon in 1919 with a one-cent per gallon gasoline tax" and within 20 years "all states had a gas tax".

As for charging 'at the point of use', Lindsey describes toll roads in the US as having "a long and chequered history", dating back to a Pennsylvania turnpike chartered in 1792. But although they were widespread in the 19th century, he says, "they rarely made money".

Originally, the method of charging on US toll roads was as simple as it was anywhere else: it involved placing people in toll booths at intervals along the road. The logical extension for high-throughput roads, such as interstates, was to build a toll plaza comprising several booths in parallel, but this could cause tailbacks while drivers searched for their money. A mechanical solution was the coin basket, which catches the change and funnels it into a coin-counter, a spin-off from banking technology.

It was only a matter of time before some sort of electronic toll collection system was developed, but despite being proposed as long ago as 1959, by the Nobel Economics Prize winner William Vickrey, it was first introduced in Bergen, Norway, in 1986. In essence, the technology is a development of the military 'identification friend or foe' (IFF) systems developed in the Second World War, but using modern-day radio-frequency identification (RFID) technology.

The most widespread system in use in the eastern US, where traffic congestion is high because of the population density, is E-ZPass, supplied by Kapsch TrafficCom. It involves fixing an RFID transponder 'tag' inside the car's windscreen which communicates, at a frequency of 915MHz, with an antenna mounted on the toll plaza. A toll is thus debited electronically from a prepaid account without having to stop the vehicle.

Probably because of the relative independence of individual American states, a number of different and incompatible electronic toll collection systems exist from Florida to California, and any prospect of a nationwide system would seem to be far in the future. It is feasible, however, that the existing network of Global Positioning Satellites (GPS) could be used to provide a national overlay for road-charging, much as it does for navigation. One of the problems, however, is a social one: privacy groups are worried that the system could be used to track users to a high level of accuracy.

Nevertheless, Oregon is again at the forefront. Noting that increases in fuel efficiency were eroding fuel tax revenues, in 2006 it introduced a pilot 'per-mile charging system', which used GPS signals and the car's odometer to measure distances driven within the state boundaries. Data was collected at gas stations, where petrol tax was deducted and the mileage fee added.

However, almost seven years later, a state-wide system has yet to be implemented. According to a US Transportation Research Board study of 2009: "Mileage charging is technically feasible, but many design and implementation details need to be worked out." Part of the problem, it says, is confirming that the technologies "work as expected" and are "acceptable to the public". It estimates that a proof-of-concept programme would take 10 to 12 years and "probably cost [around] $70m to $100m".

That's a considerable chunk of anybody's budget, but so are the costs associated with manned toll booths. According to an April 2011 report in the Gloucester County Times, a New Jersey daily: "Though 70 per cent of travelers pay their tolls electronically, state Transportation Commissioner Jim Simpson says it costs the authority double'to collect the remaining tolls manually." Apparently, 90'per cent of the New Jersey Turnpike Authority's toll booth staff earn $65,000 a year (well above the average US wage of $47,000), which could explain why those 19th century systems "rarely made money".

Interestingly, the rise of the electrically-powered vehicle could provide a boost for road-charging systems, at least in built-up areas, because of their exemption from classical tax levies. According to Joseph Rose, writing in the Oregonian newspaper, it didn't take long once the first of Nissan's all-electric LEAF cars hit Oregon's roads in 2011 for state lawmakers to consider "a road-usage charge of 1.43 cents per mile for drivers of electric and plug-in hybrid vehicles". But as in other US states, no one seems capable of actually reaching a decision. The fact that in toll plazas across the nation at least three different collection mechanisms operate in parallel – electronic passes, coin bins and that friendly palm – says it all.

Unpicking gridlock

American cities, particularly the large conurbations like Los Angeles, have become synonymous with traffic congestion and its associated pollution or 'smog' (a literal contraction of 'smoke' and 'fog' that belies its nastier chemical constituents). Indeed, the term 'gridlock' is an American invention that, although rarely used correctly elsewhere, derives from traffic queues blocking progress of vehicles on perpendicular streets in the grid-pattern design of major cities.

One solution to gridlock is to reduce traffic density by providing attractive public transportation, particularly rail-based solutions, that persuade motorists to leave their cars at home. This was a key part of the Long Range Transportation Plan (LRTP), published by Metro – the entity currently responsible for public transit in Los Angeles County – back in 2009. According to Metro, the plan takes a "three-decade look ahead to identify what transportation options best serve the county's needs and expectations". An incentive for this, according to the report, is that "the average Angelino spends 70 hours delayed in traffic per year, more than any other region in the nation".

American freeways already have High-Occupancy Vehicle (HOV) lanes, which encourage ride-sharing, but the LRTP proposes to augment these with "High-Occupancy Toll (HOT) lanes" permitting vehicles carrying fewer people than the HOV minimum to use the HOV lanes for a fee. Although this will be monitored electronically, critics might say that it is little more than a road charging system. Indeed, Metro's "three-decade look ahead" is disappointing in its lack of technological solutions. Its implementation of so-called "Intelligent Transportation Systems" appears limited to traffic monitoring, signal timing and the improvement of traffic flow.

Of course, this is better than nothing. According to the US Department of Transportation: "Peak-period travel time can be reduced by up to 11 per cent through the implementation of ITS (intelligent transport system) improvements." But it's arguable whether knocking 13 or 14 minutes off a two-hour commute will be noticeable from the driver's seat.

Vehicle-based solutions

In fairness, there's only so much the infrastructure providers can do to reduce congestion, especially where there is no viable or cost-effective alternative to a road. It's just as well that vehicle manufacturers are coming to the rescue then.

Anyone in the market for at least a mid-range car these days will be aware of the plethora of onboard electronic systems dedicated to safety and, to an extent, to removing responsibility and control from the driver. Arguably one of the simplest, and fast-becoming the standard, is the "lane departure warning system", which flashes a light and sounds a buzzer at the appropriate juncture. More complex is adaptive cruise control, which uses a front-mounted laser/radar system to monitor vehicle separation and automatically applies the brakes if it decreases beyond a set value.

It is these technologies, working together with onboard GPS and external traffic monitoring systems, that will allow the formation of relatively high-speed 'car-trains' using existing road infrastructures – the solutions the pundits say will allow us to recline our electric seats and read a newspaper for that tedious commute to work.

Their vision is supported by events. In March 2012, the state of Nevada adopted an act that authorises "the operation of autonomous vehicles on highways", as long as they carry a special red licence plate and the owners deposit a $1m bond. An 'autonomous vehicle' is typically one that "uses artificial intelligence, sensors and GPS to drive itself without the active intervention of a human operator". Florida followed in April and California in June, while according to the Centre for Internet and Society, several other states are considering similar legislation.

It's been a long time since driving a car involved following a man waving a red flag to warn unsuspecting pedestrians of the oncoming technological marvel. The degree to which our driving experience changes in the years ahead remains to be seen but, whatever happens, the evolution of our highways will continue.

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US Network Strategy

In 1916, the US Congress recognised the need for improved roads with its Federal-Aid Road Act, which sought to fund a state highway programme. Following the interruption of the First World War, this was reinstated under the Bureau of Public Roads, authorised by the Federal Highway Act of 1921 to fund a system of paved two-lane interstate highways.

So, even before Eisenhower famously championed the interstate system, which was authorised in 1956, America had its major link roads. Arguably the best known is Route 66, which ran from Chicago, Illinois, to Los Angeles, California and covered more than 2,400 miles (3,900km). It was established in 1926 and served as a major route west during the Dust Bowl crisis of the 1930s, as described in John Steinbeck's 1939 novel 'The Grapes of Wrath', though interestingly it was not completely paved until 1938.

During the Second World War, the '66 was designated a "strategic defence highway" because of the link it provided between the ordnance factories outside Chicago and the aerospace industries further west. Unsurprisingly, the heavy traffic devastated the roadbed and it had to be upgraded. Route 66 was officially removed from the US Highway System in 1985, by which time it had been replaced by the interstates.

Lesser known but longer, and a true coast-to-coast road, is the Old Spanish Trail Highway, which ran from St Augustine, Florida, to San Diego, California. It was begun in 1915 and completed in 1929, but lost its allure when the interstates offered a "better driving experience".

History of road names

The nomenclature of American roads is complex and not always consistent. Whereas turnpikes were, at least originally, toll roads, freeways are not, in fact, 'free'. The term freeway was coined by US lawyer Edward M Bassett, who distinguished between highways, parkways and freeways. Basically, property owners could build next to and gain access to highways, parkways were roads meant for recreation, and freeways were designed essentially to 'shift traffic', being free of encroaching properties and access roads. To add complexity to the definitions, dual-carriageway roads can also be termed expressways.

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