Traffic on UK roads has more than doubled since 1976 – but the road infrastructure has suffered from chronic under-investment over the same period. UK roads were ranked 30th for quality in 2014 by the Global Competitiveness Index, behind countries such as France, Germany, Spain and the Netherlands.

The government has announced a £15bn road investment strategy to tackle the issue. It focuses on the strategic road network: the motorways and A-roads that account for only 2.4% of England’s roads but carry about a third of all traffic and two-thirds of all freight. The Department for Transport (DfT) predicts traffic could rise by 46% by 2040, with the resulting congestion costing £10bn a year in lost time.

To avoid this, the hard shoulder on many existing motorways will be turned into a controlled extra lane and bottlenecks along important A-roads will be addressed. The DfT estimates that more than 1,300 lane miles will be added in more than 100 projects, including a tunnel at Stonehenge and improvements to the trans-Pennine capacity between Manchester and Sheffield. The Highways Agency will also be transformed into a government-owned company, with funding allocated on a longer-term basis.

However, Richard Burden, Labour’s shadow roads minister, claims the first road investment strategy is “a pre-election stunt with no new money”, and that its funding was outlined in 2013.

“Their roads investment record has been a chaotic series of U-turns – they claimed to support investment, but cut £4bn in planned investment and scrapped schemes in 2010, only to promise to restore them again after 2015,” he says.

Labour has backed a proposal for an independent commission to identify long-term needs in transport and establish some cross-party consensus.The Green party has gone further, pledging to scrap most of the programme and use £9bn of the money saved to subsidise public transport, supposedly cutting fares by £1.8bn a year for train and bus passengers.

Siân Berry, of the Campaign For Better Transport and a Green party councillor, believes a long-term shift away from car travel is underway, driven by things like increased urbanisation and changing attitudes toward car ownership. The DfT’s “predict and provide” approach to road planning is therefore highly flawed, she says. “We’ve seen a flattening of road traffic recently, but if all these roads get built there will be lots more induced traffic.”

Road traffic peaked in 2007 at 314.1bn vehicle miles. Professor Stephen Glaister, director of the RAC Foundation, puts the drop in road traffic volume after 2007 down to the recession, and believes increased road capacity is essential for addressing future congestion. However, he questions whether the next government will be able to afford to spend £15bn on the roads while also funding HS2 and other improvements to the rail network, and making further efforts to reduce the national debt.

“In those circumstances what would be the priorities?” he says. “The maintenance of local roads is something people feel strongly about. They’re in a terrible state in some places and getting worse – so there’s a real issue there about what choice you’re going to make.”

Councils are having to fix about 2m potholes each year despite funding cuts, while paying out £3.2m in compensation to drivers whose cars have been damaged by them. The transport secretary, Patrick McLoughlin, recently announced £6bn of funding for councils to carry out repairs, but the amount needed to properly tackle the repair backlog could be double that, according to the Asphalt Industry Alliance.

The Local Government Association (LGA) is calling for whoever forms the next government to inject an extra £1bn a year into roads maintenance – funded by investing 2 pence a litre from existing fuel duty. Councillor Peter Box, LGA transport spokesman, says England must address its “two-tier system of road funding” and points out that “very few journeys begin and end on the strategic road network and the problems of congestion cannot be effectively addressed on it in isolation”.

If it wins in the May general election, Labour has said it would prioritise fixing Britain’s pothole epidemic and work with councils to properly plan maintenance. The party also claims it will tackle cuts to local bus services, granting councils the power to award local bus licenses and support residents to run not-for-profit services.

More than 2,000 bus routes have been reduced or lost over the past five years according to the Campaign for Better Transport, with local authority funding for bus services cut by 15% (£44m). When Cumbria county council announced it would phase out £1.3m in annual subsidies to private bus operators, Stagecoach cut or reduced 70 routes. Seven local authorities – Hartlepool, Stockton-on-Tees, Darlington, Stoke-on-Trent, Luton, Southend-on-Sea and Wrexham – now spend nothing on supported bus services. Yet fares have been rising above inflation.

In London, it’s a different story. The capital’s bus system, which accounts for almost half of all bus journeys in England, remained in the control of Transport for London (TfL) when the rest of the country’s network was deregulated in the 1980s. Rather than being cut, bus services increased by a third in the capital between 2001 and 2011. TfL has also been able press ahead with an integrated transport strategy – in some areas road capacity has actually been reduced in favour of bus and cycle lanes or pedestrians.

Transport for Greater Manchester will soon get similar transport powers as part of the government’s plan to create a northern powerhouse of thriving northern cities, allowing it to make better long-term infrastructure plans and introduce its own Oyster-style smart ticketing system across the tram and bus network.

Jon Lamonte, chief executive of the Transport for Greater Manchester, says devolved transport power is “absolutely fundamental” for economic growth, and stresses the importance of developments like electric cars, open data and smart traffic monitoring systems in delivering a full-integrated, responsive transport network. “If you can give really good, real-time information to customers no matter where they are, that’s the way to do things,” he says.

More in the series on transport policy post May 2015:
• Full steam ahead: how will the election result affect UK rail passengers?
• Up ahead: how will the election result affect UK air passengers?

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