Transport for London (TfL) has admitted that its funding system for roads is unsustainable and it has no long-term solution.

TfL's five-year business plan up to 2023/24 revealed that in 2018/19 it has budgeted the cost of maintaining its roads at twice that of income for this area - £600m compared to £317m.

'London is the only part of the UK without routine government funding for its strategic road network. We are therefore left with subsidising this maintenance activity from public transport fares income. A long-term funding source for our roads must be identified,' TfL said.

It added that there is no clear end in sight to its road maintenance cuts.

'Last year we took the difficult decision to significantly reduce the programme of proactive road maintenance, on both our roads and borough roads, while maintaining safety as our top priority. Despite driving record efficiencies, we have had to continue this position.'

There are signs that more income could come in from roads through air quality charges but this could be swallowed up by TfL's wider costs - particularly related to the Crossrail delay.

'In October 2021 the Ultra Low Emission Zone will be extended to the North and South Circular roads for all vehicles. By the end of 2019 TfL will introduce a further five Low Emission Bus Zones, bringing the total number to 12 and cleaning up the air in high streets across the capital. Through these and other far-reaching measures TfL will continue to play a key role in cleaning up London’s toxic air and addressing the public health crisis that it has caused.'

In terms of safety, TfL is rolling out a major programme of 20mph speed limits. Around 8.9km of TfL roads in central London will be converted to 20mph zones by 2020, including all roads within congestion charge zone by May 2020.

Beyond 2020, TfL will expand this approach to lower the speed limit on the Inner Ring Road and a number of outer London town centres, it said.

The news follows 3,881 people being killed or seriously injured on London’s roads in 2017. This is an estimated 39% reduction against the 2005-09 baseline, following a one percentage point increase between 2016 and 2017.

TfL also plans to create half of the 73 Safer Junctions by May 2020 and 'deliver a world leading road management system to control London's traffic signals by 2020'.

On the issue of disruption, TfL said: 'We have established a new metric to better reflect the impact of disruption on our roads, with each year baselined against the previous year’s performance.'

However it added that motorists could continue to expect difficulties due to planned upgrade projects and utilities works.