After years of campaigning by the London Cycling Campaign and many others, the Mayor Boris Johnson has finally agreed to a 20mph speed limit on Blackfriars Bridge, as well as across London Bridge.

An 18-month trial expected to start soon will see motor traffic speeds limited to 20mph on both central London bridges, in accordance with recommendations made by a Transport for London report in 2008.

The measure ties in with the City of London's proposed area-wide 20mph speed limit, and streets approaching Blackfriars Bridge will also have 20mph limits, including New Bridge Street and Farringdon Street (up to Charterhouse Street).

The London Bridge 20mph measure will be extended to King William Street, Gracechurch Street, Bishopsgate, Norton Folgate (up to Worship Street).

LCC Chief Executive Ashok Sinha said, "Although this change of heart has taken a long to time to achieve, we nonetheless welcome the trial of a 20mph speed limit on two central London bridges.

"Reducing speed in this way is proven to increase safety with very minor impacts on motor traffic, and we look forward to seeing 20mph limits introduced on all central London bridges."

A study published in the the British Medical Journal has shown that 20mph speed limits are associated with a greater than 40% reduction in deaths and serious injuries for all road users, and can play a major part in improving safety and comfort for cycling and walking.

Blackfriars Bridge was the site of three major protest rides in 2011 (one, two, three (pictured)), when LCC organised for thousands of Londoners on bicycles to take over the bridge during rush hour in protest at the Mayor’s refusal to back 20mph or to redesign the flawed northern junction to make it safe for cycling.

Many of our supporters also took part in our 20mph photo petition in 2011 to persuade London Assembly to vote for the measure.

As well as this week’s announcement of a 20mph trial on Blackfriars Bridge, there’s also a strong expectation that the proposed North-South Superhighway, announced by Andrew Gilligan in 2013, will require the junction outside Blackfriars station to be redesigned to provide protected space for cycling.

At present, anyone cycling northbound across Blackfriars Bridge and wanting to turn right into Queen Victoria Street has to cross three lanes of potentially fast-moving traffic.

There have been many serious collisions, including fatal and near-fatal crashes at Blackfriars, and in its current form it fails to provide anywhere near the required degree of safety or comfort.

It was redesigned in 2011, to a standard that LCC and other campaigners said was deeply unsatisfactory considering the high volumes of cycle traffic using the bridge: cyclists make up one third of traffic during the morning rush hour.

A motion passed at LCC’s 2013 AGM called for no London cyclist to be forced to share road space with motor traffic travelling over 20mph or 2000 PCUs per hour (passenger car units).

When those boundaries are exceeded, then authorities have a choice to either separate cyclists using kerbed cycle lanes, or to reduce speeds and volumes of motor traffic to acceptable levels.

In 2011 we published our own design for the junction, which provide protected lanes for cycling, cyclist-specific traffic light phases, and removed the motorway-style sliproads, creating a more harmonious environment for cyclists and pedestrians.