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How much does your road weigh?
The ways roads are used, with ever larger and heavier vehicles, have dramatic consequences on the environment – and electric cars are not the answer
Today, there is an average of 37 tonnes of road per inhabitant of the planet. The weight of the road network alone accounts for a third of all construction worldwide, and has grown exponentially in the 20th century. There is 10 times more bitumen, in mass, than there are living animals. Yet growth in the mass of roads does not automatically correspond to population growth, or translate into increased length of road networks. In wealthier countries, the number of metres of road per inhabitant has actually fallen over the last century. In the United States, for instance, between 1905 and 2015 the length of the network increased by a factor of 1.75 and the population by a factor of 3.8, compared with 21 for the mass of roads. Roads have become wider and, above all, much thicker. To understand the evolution of these parameters, and their environmental impact, it is helpful to trace the different stages in the life of the motorway.
Until the early 20th century, roads were used for various modes of transport, including horses, bicycles, pedestrians and trams; as a result of the construction of railways, road traffic even declined in some European countries in the 19th century. The main novelty brought by the motorway was that they would be reserved for motorised traffic. In several languages, the word itself – autostrada, autobahn, autoroute or motorway – speaks of this exclusivity.
Roman roads varied from simple corduroy roads, made by placing logs perpendicular to the direction of the road over a low or swampy area, to paved roads, as this engraving from Jean Rondelet’s 19th‑century Traité Théorique et Pratique de l’Art de Bâtir shows. Using deep roadbeds of tamped rubble as an underlying layer to ensure that they kept dry, major roads were often stone-paved, metalled, cambered for drainage and flanked by footpaths, bridleways and drainage ditches
Like any major piece of infrastructure, motorways became the subject of ideological discourse, long before any shovel hit the ground; politicians underlined their role in the service of the nation, how they would contribute to progress, development, the economy, modernity and even civilisation. The inauguration ceremony for the construction of the first autostrada took place in March 1923, presided over by Italy’s prime minister Benito Mussolini. The second major motorway programme was announced by the Nazi government in 1933, with a national network planned to be around 7,000 kilometres long. In his 2017 book Driving Modernity: Technology, Experts, Politics, and Fascist Motorways, 1922–1943, historian Massimo Moraglio shows how both programmes were used as propaganda tools by the regimes, most notably at the international road congresses in Milan in 1926 and Munich in 1934. In the European postwar era, the notion of the ‘civilising’ effect of roads persevered. In 1962, Valéry Giscard d’Estaing, then‑secretary of state for finances and later president of France, argued that expanded motorways would bring ‘progress, activity and life’.
This discourse soon butted up against the realities of how motorways affected individuals and communities. In his 2011 book Fighting Traffic: The Dawn of the Motor Age in the American City, Peter D Norton explores the history of resistance to the imposition of motorised traffic in North American cities. Until the 1920s, there was a perception that cars were dangerous newcomers, and that other street and road uses – especially walking – were more legitimate. Cars were associated with speed and danger; restrictions on motorists, especially speed limits, were routine.
Built between 1962 and 1970, the Westway was London’s first urban motorway, elevated above the city to use less land. Construction workers are seen stressing the longitudinal soffit cables inside the box section of the deck units to achieve the bearing capacity necessary to carry the weight of traffic
Credit: Heritage Image Partnership Ltd / Alamy
To gain domination over cities, motor vehicles had to win priority over other street uses. Rather than restricting the flow of vehicles to minimise the risk of road accidents, a specific infrastructure was dedicated to them: both inner‑city roads and motorways. Cutting through the landscape, the motorway had, by definition, to be inaccessible by any other means of transport than motorised vehicle. To guarantee the fluidity of traffic, the construction of imposing bridges, tunnels and interchanges is necessary, particularly at junctions with other roads, railways or canals. This prioritisation of one type of user inevitably impacts journeys for others; as space is fragmented, short journeys are lengthened for those trying to navigate space by foot or bicycle.
Enabling cars to drive at around 110–140km/h on motorways, as modern motorways do, directly impacts their design, with major environmental effects: the gradient has to be gentle, the curves longand the lanes wide, to allow vehicles to overtake each other safely. As much terrain around the world is not naturally suited to these requirements, the earthworks are considerable: in France, the construction of a metre of highway requires moving some 100m3 of earth, and when the soil is soft, full of clay or peat, it is made firmer with hydraulic lime and cement before the highway’s first sub‑layers are laid. This material cost reinforces the criticisms levelled in the 1960s, by the likes of Jane Jacobs and Lewis Mumford, at urban planning that prioritised the personal motor vehicle.
When roads are widened to accommodate more traffic, buildings are sliced and demolished, as happened in Dhaka’s Bhasantek Road in 2021
Credit: Dhaka Tribune
Once built, the motorway is never inert. Motorway projects today generally anticipate future expansion, and include a large median strip of 12m between the lanes, with a view to adding new ones. Increases in speed and vehicle sizes have also translated into wider lanes, from 2.5m in 1945 to 3.5m today. The average contemporary motorway footprint is therefore 100 square metres per linear metre. Indeed, although the construction of a road is supposed to reduce congestion, it also generates new traffic and, therefore, new congestion. This is the principle of ‘induced traffic’: the provision of extra road capacity results in a greater volume of traffic.
The Katy Freeway in Texas famously illustrates this dynamic. Built as a regular six‑lane highway in the 1960s, it was called the second worst bottleneck in the nation by 2004, wasting 25 million hours a year of commuter time. In 2011, the state of Texas invested USbillion to fix this problem, widening the road to a staggering total of 26 lanes. By 2014, the morning and afternoon traffic had both increased again. The vicious circle based on the induced traffic has been empirically demonstrated in most countries: traffic has continued to increase and congestion remains unresolved, leading to ever-increasing emissions. In the EU, transport is the only sector where greenhouse gas emissions have increased in the past three decades, rising 33.5 per cent between 1990 and 2019. Transport accounts for around a fifth of global CO₂ emissions today, with three quarters of this figure linked to road transport.
Houston’s Katy Freeway is one of the world’s widest motorways, with 26 lanes. Its last expansion, in 2008, was initially hailed as a success, but within five years, peak travel times were longer than before the expansion – a direct illustration of the principle of induced traffic
Credit: Smiley N Pool / Houston Chronicle / Getty
Like other large transport infrastructures such as ports and airports, motorways are designed for the largest and heaviest vehicles. Engineers, road administrations and politicians have known since the 1950s that one truck represents millions of cars: the impact of a vehicle on the roadway is exponential to its weight – an online ‘road damage calculator’ allows you to compare the damage done by different types of vehicles to the road. Over the years, heavier and heavier trucks have been authorised to operate on roads: from 8‑tonne trucks in 1945 to 44 tonnes nowadays. The European Parliament adopted a revised directive on 12 March 2024 authorising mega‑trucks to travel on European roads; they can measure up to 25 metres and weigh up to 60 tonnes, compared with the previous limits of 18.75 metres and 44 tonnes. This is a political and economic choice with considerable material effects: thickness, rigidity of sub‑bases and consolidation of soil and subsoil with lime and cement. Altogether, motorways are 10 times thicker than large roads from the late 19th century. In France, it takes an average of 30 tonnes of sand and aggregate to build one linear metre of motorway, 100 times more than cement and bitumen.
The material history of road networks is a history of quarrying and environmental damage. The traces of roads can also be seen in rivers emptied of their sediment, the notches of quarries in the hills and the furrows of dredgers extracting sand from the seabed. This material extraction, arguably the most significant in human history, has dramatic ecological consequences for rivers, groundwater tables, the rise of sea levels and saltwater in farmlands, as well as biodiversity. As sand is ubiquitous and very cheap, the history of roads is also the history of a local extractivism and environmental conflicts around the world.
Shoving and rutting is the bulging and rippling of the pavement surface. Once built, roads require extensive maintenance – the heavier the vehicles, the quicker the damage. From pothole repair to the full resurfacing of a road, maintenance contributes to keeping road users safe
Credit: Yakov Oskanov / Alamy
Once roads are built and extended, they need to be maintained to support the circulation of lorries and, by extension, commodities. This stage is becoming increasingly important as rail freight, which used to be important in countries such as France and the UK, is declining, accounting for no more than 10 per cent of the transport of commodities. Engineers might judge that a motorway is destined to last 20 years or so, but this prognosis will be significantly reduced with heavy traffic. The same applies to the thousands of motorway bridges: in the UK, nearly half of the 9,000 highway bridges are in poor condition; in France, 7 per cent of the 12,000 bridges are in danger of collapsing, as did Genoa’s Morandi bridge in 2018. If only light vehicles drove on it, this infrastructure would last much longer.
This puts into perspective governments’ insistence on ‘greening’ the transport sector by targeting CO2 emissions alone, typically by promoting the use of electric vehicles. Public policies prioritising EVs do nothing to change the mass of roads or the issue of their maintenance – even if lorries were to run on clean air, massive quarrying would still be necessary. A similar argument plays out with regard to canals and ports, which have been constantly widened and deepened for decades to accommodate ever-larger oil tankers or container ships. The simple operation of these infrastructures, dimensioned for the circulation of commodities and not humans, requires permanent dredging of large volumes. The environmental problem of large transport infrastructure goes beyond the type of energy used: it is, at its root, free and globalised trade.
‘The material life cycle of motorways is relentless: constructing, maintaining, widening, thickening, repairing’
As both a material and ideological object, the motorway fixes certain political choices in the landscape. Millions of kilometres of road continue to be asphalted, widened and thickened around the world to favour cars and lorries. In France, more than 80 per cent of today’s sand and aggregate extraction is used for civil engineering works – the rest goes to buildings. Even if no more buildings, roads or other infrastructures were to be built, phenomenal quantities of sand and aggregates would still need to be extracted in order to maintain existing road networks. The material life cycle of motorways is relentless: constructing, maintaining, widening, thickening, repairing, adding new structures such as wildlife crossings, more maintaining.
Rising traffic levels are always deemed positive by governments for a country’s economy and development. As Christopher Wells shows in his 2014 book Car Country: An Environmental History, car use becomes necessary in an environment where everything has been planned for the car, from the location of public services and supermarkets to residential and office areas. Similarly, when an entire economy is based on globalised trade and just‑in‑time logistics, the lorry and the container ship become vital.
The final stage in the life of a piece of motorway infrastructure is dismantling. Like the other stages, this one is not a natural outcome but the fruit of political choices – which should be democratic – regarding how we wish to use existing roads. Dismantling, which is essential if we are to put an end to the global extractivism of sand and aggregates, does not mean destruction: if bicycles and pedestrians were to use them instead, maintenance would be minimal. This final stage requires a paradigm shift away from the eternal adaptation to increasing traffic. Replacing cars and lorries with public transport and rail freight would be a first step. But above all, a different political and spatial organisation of economic activities is necessary, and ultimately, an end to globalised, just-in-time trade and logistics.
In 1978, a row of cars parked at a shopping centre in Connecticut was buried under a thick layer of gooey asphalt. The Ghost Parking Lot, one of the first projects by James Wines’ practice SITE, became a playground for skateboarders until it was removed in 2003. Images of this lumpy landscape serve as allegories of the damage caused by reliance on the automobile
Credit: Project by SITE
Lead image: Some road damage is beyond repair, as when a landslide caused a large chunk of the Gothenburg–Oslo motorway to collapse in 2023. Such dramatic events remind us of both the fragility of these seemingly robust infrastructures, and the damage that extensive construction does to the planet. Credit: Hanna Brunlöf Windell / TT / Shutterstock
2025-06-03
Reuben J Brown
Share
#how #much #does #your #road
How much does your road weigh?
The ways roads are used, with ever larger and heavier vehicles, have dramatic consequences on the environment – and electric cars are not the answer
Today, there is an average of 37 tonnes of road per inhabitant of the planet. The weight of the road network alone accounts for a third of all construction worldwide, and has grown exponentially in the 20th century. There is 10 times more bitumen, in mass, than there are living animals. Yet growth in the mass of roads does not automatically correspond to population growth, or translate into increased length of road networks. In wealthier countries, the number of metres of road per inhabitant has actually fallen over the last century. In the United States, for instance, between 1905 and 2015 the length of the network increased by a factor of 1.75 and the population by a factor of 3.8, compared with 21 for the mass of roads. Roads have become wider and, above all, much thicker. To understand the evolution of these parameters, and their environmental impact, it is helpful to trace the different stages in the life of the motorway.
Until the early 20th century, roads were used for various modes of transport, including horses, bicycles, pedestrians and trams; as a result of the construction of railways, road traffic even declined in some European countries in the 19th century. The main novelty brought by the motorway was that they would be reserved for motorised traffic. In several languages, the word itself – autostrada, autobahn, autoroute or motorway – speaks of this exclusivity.
Roman roads varied from simple corduroy roads, made by placing logs perpendicular to the direction of the road over a low or swampy area, to paved roads, as this engraving from Jean Rondelet’s 19th‑century Traité Théorique et Pratique de l’Art de Bâtir shows. Using deep roadbeds of tamped rubble as an underlying layer to ensure that they kept dry, major roads were often stone-paved, metalled, cambered for drainage and flanked by footpaths, bridleways and drainage ditches
Like any major piece of infrastructure, motorways became the subject of ideological discourse, long before any shovel hit the ground; politicians underlined their role in the service of the nation, how they would contribute to progress, development, the economy, modernity and even civilisation. The inauguration ceremony for the construction of the first autostrada took place in March 1923, presided over by Italy’s prime minister Benito Mussolini. The second major motorway programme was announced by the Nazi government in 1933, with a national network planned to be around 7,000 kilometres long. In his 2017 book Driving Modernity: Technology, Experts, Politics, and Fascist Motorways, 1922–1943, historian Massimo Moraglio shows how both programmes were used as propaganda tools by the regimes, most notably at the international road congresses in Milan in 1926 and Munich in 1934. In the European postwar era, the notion of the ‘civilising’ effect of roads persevered. In 1962, Valéry Giscard d’Estaing, then‑secretary of state for finances and later president of France, argued that expanded motorways would bring ‘progress, activity and life’.
This discourse soon butted up against the realities of how motorways affected individuals and communities. In his 2011 book Fighting Traffic: The Dawn of the Motor Age in the American City, Peter D Norton explores the history of resistance to the imposition of motorised traffic in North American cities. Until the 1920s, there was a perception that cars were dangerous newcomers, and that other street and road uses – especially walking – were more legitimate. Cars were associated with speed and danger; restrictions on motorists, especially speed limits, were routine.
Built between 1962 and 1970, the Westway was London’s first urban motorway, elevated above the city to use less land. Construction workers are seen stressing the longitudinal soffit cables inside the box section of the deck units to achieve the bearing capacity necessary to carry the weight of traffic
Credit: Heritage Image Partnership Ltd / Alamy
To gain domination over cities, motor vehicles had to win priority over other street uses. Rather than restricting the flow of vehicles to minimise the risk of road accidents, a specific infrastructure was dedicated to them: both inner‑city roads and motorways. Cutting through the landscape, the motorway had, by definition, to be inaccessible by any other means of transport than motorised vehicle. To guarantee the fluidity of traffic, the construction of imposing bridges, tunnels and interchanges is necessary, particularly at junctions with other roads, railways or canals. This prioritisation of one type of user inevitably impacts journeys for others; as space is fragmented, short journeys are lengthened for those trying to navigate space by foot or bicycle.
Enabling cars to drive at around 110–140km/h on motorways, as modern motorways do, directly impacts their design, with major environmental effects: the gradient has to be gentle, the curves longand the lanes wide, to allow vehicles to overtake each other safely. As much terrain around the world is not naturally suited to these requirements, the earthworks are considerable: in France, the construction of a metre of highway requires moving some 100m3 of earth, and when the soil is soft, full of clay or peat, it is made firmer with hydraulic lime and cement before the highway’s first sub‑layers are laid. This material cost reinforces the criticisms levelled in the 1960s, by the likes of Jane Jacobs and Lewis Mumford, at urban planning that prioritised the personal motor vehicle.
When roads are widened to accommodate more traffic, buildings are sliced and demolished, as happened in Dhaka’s Bhasantek Road in 2021
Credit: Dhaka Tribune
Once built, the motorway is never inert. Motorway projects today generally anticipate future expansion, and include a large median strip of 12m between the lanes, with a view to adding new ones. Increases in speed and vehicle sizes have also translated into wider lanes, from 2.5m in 1945 to 3.5m today. The average contemporary motorway footprint is therefore 100 square metres per linear metre. Indeed, although the construction of a road is supposed to reduce congestion, it also generates new traffic and, therefore, new congestion. This is the principle of ‘induced traffic’: the provision of extra road capacity results in a greater volume of traffic.
The Katy Freeway in Texas famously illustrates this dynamic. Built as a regular six‑lane highway in the 1960s, it was called the second worst bottleneck in the nation by 2004, wasting 25 million hours a year of commuter time. In 2011, the state of Texas invested USbillion to fix this problem, widening the road to a staggering total of 26 lanes. By 2014, the morning and afternoon traffic had both increased again. The vicious circle based on the induced traffic has been empirically demonstrated in most countries: traffic has continued to increase and congestion remains unresolved, leading to ever-increasing emissions. In the EU, transport is the only sector where greenhouse gas emissions have increased in the past three decades, rising 33.5 per cent between 1990 and 2019. Transport accounts for around a fifth of global CO₂ emissions today, with three quarters of this figure linked to road transport.
Houston’s Katy Freeway is one of the world’s widest motorways, with 26 lanes. Its last expansion, in 2008, was initially hailed as a success, but within five years, peak travel times were longer than before the expansion – a direct illustration of the principle of induced traffic
Credit: Smiley N Pool / Houston Chronicle / Getty
Like other large transport infrastructures such as ports and airports, motorways are designed for the largest and heaviest vehicles. Engineers, road administrations and politicians have known since the 1950s that one truck represents millions of cars: the impact of a vehicle on the roadway is exponential to its weight – an online ‘road damage calculator’ allows you to compare the damage done by different types of vehicles to the road. Over the years, heavier and heavier trucks have been authorised to operate on roads: from 8‑tonne trucks in 1945 to 44 tonnes nowadays. The European Parliament adopted a revised directive on 12 March 2024 authorising mega‑trucks to travel on European roads; they can measure up to 25 metres and weigh up to 60 tonnes, compared with the previous limits of 18.75 metres and 44 tonnes. This is a political and economic choice with considerable material effects: thickness, rigidity of sub‑bases and consolidation of soil and subsoil with lime and cement. Altogether, motorways are 10 times thicker than large roads from the late 19th century. In France, it takes an average of 30 tonnes of sand and aggregate to build one linear metre of motorway, 100 times more than cement and bitumen.
The material history of road networks is a history of quarrying and environmental damage. The traces of roads can also be seen in rivers emptied of their sediment, the notches of quarries in the hills and the furrows of dredgers extracting sand from the seabed. This material extraction, arguably the most significant in human history, has dramatic ecological consequences for rivers, groundwater tables, the rise of sea levels and saltwater in farmlands, as well as biodiversity. As sand is ubiquitous and very cheap, the history of roads is also the history of a local extractivism and environmental conflicts around the world.
Shoving and rutting is the bulging and rippling of the pavement surface. Once built, roads require extensive maintenance – the heavier the vehicles, the quicker the damage. From pothole repair to the full resurfacing of a road, maintenance contributes to keeping road users safe
Credit: Yakov Oskanov / Alamy
Once roads are built and extended, they need to be maintained to support the circulation of lorries and, by extension, commodities. This stage is becoming increasingly important as rail freight, which used to be important in countries such as France and the UK, is declining, accounting for no more than 10 per cent of the transport of commodities. Engineers might judge that a motorway is destined to last 20 years or so, but this prognosis will be significantly reduced with heavy traffic. The same applies to the thousands of motorway bridges: in the UK, nearly half of the 9,000 highway bridges are in poor condition; in France, 7 per cent of the 12,000 bridges are in danger of collapsing, as did Genoa’s Morandi bridge in 2018. If only light vehicles drove on it, this infrastructure would last much longer.
This puts into perspective governments’ insistence on ‘greening’ the transport sector by targeting CO2 emissions alone, typically by promoting the use of electric vehicles. Public policies prioritising EVs do nothing to change the mass of roads or the issue of their maintenance – even if lorries were to run on clean air, massive quarrying would still be necessary. A similar argument plays out with regard to canals and ports, which have been constantly widened and deepened for decades to accommodate ever-larger oil tankers or container ships. The simple operation of these infrastructures, dimensioned for the circulation of commodities and not humans, requires permanent dredging of large volumes. The environmental problem of large transport infrastructure goes beyond the type of energy used: it is, at its root, free and globalised trade.
‘The material life cycle of motorways is relentless: constructing, maintaining, widening, thickening, repairing’
As both a material and ideological object, the motorway fixes certain political choices in the landscape. Millions of kilometres of road continue to be asphalted, widened and thickened around the world to favour cars and lorries. In France, more than 80 per cent of today’s sand and aggregate extraction is used for civil engineering works – the rest goes to buildings. Even if no more buildings, roads or other infrastructures were to be built, phenomenal quantities of sand and aggregates would still need to be extracted in order to maintain existing road networks. The material life cycle of motorways is relentless: constructing, maintaining, widening, thickening, repairing, adding new structures such as wildlife crossings, more maintaining.
Rising traffic levels are always deemed positive by governments for a country’s economy and development. As Christopher Wells shows in his 2014 book Car Country: An Environmental History, car use becomes necessary in an environment where everything has been planned for the car, from the location of public services and supermarkets to residential and office areas. Similarly, when an entire economy is based on globalised trade and just‑in‑time logistics, the lorry and the container ship become vital.
The final stage in the life of a piece of motorway infrastructure is dismantling. Like the other stages, this one is not a natural outcome but the fruit of political choices – which should be democratic – regarding how we wish to use existing roads. Dismantling, which is essential if we are to put an end to the global extractivism of sand and aggregates, does not mean destruction: if bicycles and pedestrians were to use them instead, maintenance would be minimal. This final stage requires a paradigm shift away from the eternal adaptation to increasing traffic. Replacing cars and lorries with public transport and rail freight would be a first step. But above all, a different political and spatial organisation of economic activities is necessary, and ultimately, an end to globalised, just-in-time trade and logistics.
In 1978, a row of cars parked at a shopping centre in Connecticut was buried under a thick layer of gooey asphalt. The Ghost Parking Lot, one of the first projects by James Wines’ practice SITE, became a playground for skateboarders until it was removed in 2003. Images of this lumpy landscape serve as allegories of the damage caused by reliance on the automobile
Credit: Project by SITE
Lead image: Some road damage is beyond repair, as when a landslide caused a large chunk of the Gothenburg–Oslo motorway to collapse in 2023. Such dramatic events remind us of both the fragility of these seemingly robust infrastructures, and the damage that extensive construction does to the planet. Credit: Hanna Brunlöf Windell / TT / Shutterstock
2025-06-03
Reuben J Brown
Share
#how #much #does #your #road
