A sign indicating the begining of the congestion charging zone, which is managed by Capita, is seen in London, Britain, January 31, 2018. REUTERS/Toby Melville

A sign indicating the begining of the congestion charging zone, which is managed by Capita, is seen in London, Britain, January 31, 2018. REUTERS/Toby Melville

Umbrellas for protection against pepper spray are stacked on a barricade set up by protesters, as police stand guard a blocked road at Mongkok shopping district in Hong Kong October 18, 2014. Hong Kong pro-democracy activists recaptured parts of a core protest zone early on Saturday, defying riot police who had tried to disperse them with pepper spray and baton charges. REUTERS/Tyrone Siu (CHINA - Tags: POLITICS CIVIL UNREST BUSINESS)

A pro-democracy protester sleeps on a barricade as police stand guard behind him on a blocked road at Mongkok shopping district in Hong Kong October 18, 2014. Hong Kong pro-democracy activists recaptured parts of a core protest zone early on Saturday, defying riot police who had tried to disperse them with pepper spray and baton charges. REUTERS/Tyrone Siu (CHINA - Tags: POLITICS CIVIL UNREST BUSINESS TPX IMAGES OF THE DAY)

Protesters block a public transport bus on a road in the Mongkok shopping district of Hong Kong late October 17, 2014. Hong Kong riot police used pepper spray and baton charged pro-democracy protesters who mobilised en masse on Friday evening after a pre-dawn clearance of a major protest zone in the Chinese-controlled financial hub. REUTERS/Bobby Yip (CHINA - Tags: POLITICS CIVIL UNREST TRANSPORT)

Thousands of protesters block Nathan Road after the police retreated, following failed attempts to remove the protesters from the site, in the Mongkok shopping district of Hong Kong late October 17, 2014. Hong Kong riot police used pepper spray and baton charged pro-democracy protesters who mobilised en masse on Friday evening after a pre-dawn clearance of a major protest zone in the Chinese-controlled financial hub.REUTERS/Bobby Yip (CHINA - Tags: POLITICS BUSINESS EDUCATION CIVIL UNREST)

Protesters wearing masks stand in front of a sign that used to show Nathan Road, which has been covered over and now reads, "True Democracy, Where is the True Universal Suffrage?" during a confrontation at Mongkok shopping district in Hong Kong October 17, 2014. Hong Kong riot police used pepper spray and baton as they charged crowds of pro-democracy protesters on Friday evening as tension escalated after a pre-dawn clearance of a major protest zone in the Chinese-controlled financial hub. REUTERS/Bobby Yip (CHINA - Tags: POLITICS BUSINESS EDUCATION CIVIL UNREST TPX IMAGES OF THE DAY)

Pro-democracy protesters scuffle with riot police on a blocked road at Mongkok shopping district in Hong Kong October 17, 2014. Hundreds of Hong Kong police staged their biggest raid yet on a pro-democracy protest camp before dawn on Friday, charging down student-led activists who have held an intersection in one of their main protest zones for more than three weeks. REUTERS/Tyrone Siu (CHINA - Tags: POLITICS CIVIL UNREST)

Anti-Occupy Central protesters shout at pro-democracy protesters on a blocked road at Mongkok shopping district in Hong Kong October 17, 2014. Hundreds of Hong Kong police staged their biggest and boldest raid yet on a pro-democracy protest camp before dawn on Friday, charging down student-led activists who have held a key intersection in one of the main protest zones for more than three weeks. REUTERS/Tyrone Siu (CHINA - Tags: POLITICS CIVIL UNREST)

Pro-democracy protesters sit on a blocked road at Mongkok shopping district in Hong Kong October 17, 2014. Hundreds of Hong Kong police staged their biggest and boldest raid yet on a pro-democracy protest camp before dawn on Friday, charging down student-led activists who have held a key intersection in one of the main protest zones for more than three weeks. REUTERS/Tyrone Siu (CHINA - Tags: POLITICS CIVIL UNREST)

Police put in place barriers to separate local residents and pro-democracy protesters on a blocked road at Mongkok shopping district in Hong Kong October 17, 2014. Hundreds of Hong Kong police staged their biggest and boldest raid yet on a pro-democracy protest camp before dawn on Friday, charging down student-led activists who have held a key intersection in one of the main protest zones for more than three weeks. REUTERS/Tyrone Siu (CHINA - Tags: POLITICS CIVIL UNREST)

Pro-democracy protesters rest on a blocked road at Mongkok shopping district in Hong Kong October 17, 2014. Hundreds of Hong Kong police staged their biggest and boldest raid yet on a pro-democracy protest camp before dawn on Friday, charging down student-led activists who have held a key intersection in one of the main protest zones for more than three weeks. REUTERS/Tyrone Siu (CHINA - Tags: POLITICS CIVIL UNREST)

A car drives pass a congestion charge sign on a street near Earls Court Road in west London February 19, 2007. The western extension to the London congestion charging zone comes into force on Monday and will cost 8 pounds ($15.60) per day. REUTERS/Alessia Pierdomenico (BRITAIN)

A passer-by walks over a congestion charge sign on a street near Earls Court Road in west London February 19, 2007. The western extension to the London congestion charging zone comes into force on Monday and will cost 8 pounds ($15.60) per day. REUTERS/Alessia Pierdomenico (BRITAIN)

A congestion charge pay reminder sign is displayed in London February 19, 2007. The western extension to the London congestion charging zone comes into force on Monday and will cost 8 pounds ($15.60) per day. REUTERS/Alessia Pierdomenico (BRITAIN)

A congestion charge pay reminder sign is displayed in London February 19, 2007. The western extension to the London congestion charging zone comes into force on Monday and will cost 8 pounds ($15.60) per day. REUTERS/Alessia Pierdomenico (BRITAIN)

A congestion charge pay reminder sign is seen in London February 19, 2007. The western extension to the London congestion charging zone comes into force on Monday and will cost 8 pounds ($15.6) per day. REUTERS/Alessia Pierdomenico (BRITAIN)

Motorists drive past the new congestion zone symbols on the road at Chelsea Bridge in London February 16, 2007. The western extension to the London congestion charging zone is due to come into force on February 19 and will cost 8 pound ($15.6) a day. REUTERS/Toby Melville (BRITAIN)

A new congestion charge sign is erected on the road at Chelsea Bridge in London February 16, 2007. The western extension to the London congestion charging zone is due to come into force on February 19 and will cost 8 pound ($15.6) a day. REUTERS/Toby Melville (BRITAIN)

New congestion charge signs are erected on a road at Chelsea Bridge in London February 16, 2007. The western extension to the London congestion charging zone is due to come into force on February 19 and will cost 8 pound ($15.6) a day. REUTERS/Toby Melville (BRITAIN)

A road symbol showing the congestion zone 'C' is seen in southwest London February 13, 2007. The western extension to the London congestion charging zone is due to come into force February 19 and will cost 8GBP-a-day. Picture taken using time-exposure. REUTERS/Dylan Martinez (BRITAIN)

A road symbol showing the congestion zone 'C' is seen in southwest London February 13, 2007. The western extension to the London congestion charging zone is due to come into force February 19 and will cost 8GBP-a-day. Picture taken using time-exposure. REUTERS/Dylan Martinez (BRITAIN)

A road symbol showing the congestion zone 'C' is seen in southwest London February 13, 2007. The western extension to the London congestion charging zone is due to come into force February 19 and will cost 8GBP-a-day. Picture taken with time-exposure. REUTERS/Dylan Martinez (BRITAIN)

A man crosses the road over a "C" sign marking the start of the congestion charging zone in central London, February 17, 2003. The world's biggest traffic congestion charge scheme went live at 0700 GMT in London on Monday, using 800 cameras and 400 points in and around an eight-square-mile (21square km) area of the city centre to monitor the licence plates of the 250,000 motorists who drive in the area each day, who will each pay a fee of five pounds a day.

A woman crosses the road over a "C" sign marking the start of the congestion charging zone in central London, February 17, 2003. The world's biggest traffic congestion charge scheme went live at 0700 GMT in London on Monday, using 800 cameras and 400 points in and around an eight-square-mile (21square km) area of the city centre to monitor the licence plates of the 250,000 motorists who drive in the area each day, who will each pay a fee of five pounds a day.

Cyclists ride past "C" signs marking the start of the congestion charging zone in central London, February 17, 2003. The world's biggest traffic congestion charge scheme went live at 0700 GMT in London on Monday, using 800 cameras and 400 points in and around an eight-square-mile (21square km) area of the city centre to monitor the licence plates of the 250,000 motorists who drive in the area each day, who will each pay a fee of five pounds a day. TPORT REUTERS/Russell Boyce RUS/ASA

Motorists drive over "C" signs marking the start of the congestion charging zone before the scheme comes into force in central London February 17, 2003. The world's biggest traffic congestion charge scheme went live at 0700 GMT in London on Monday, using 800 cameras and 400 points in and around an eight-square-mile (21square km) area of the city centre to monitor the licence plates of the 250,000 motorists who drive in the area each day, who will each pay a fee of five pounds ($8) a day. TPORT REUTERS/Russell Boyce Pictures of the month February 2003 RUS/ASA/jm

A small number of cars queue on the link road in east London as a full
moon rises over them during the rush hour, February 17, 2003. Initial
estimates claim a reduction of 25% of traffic in central London on the
first day of the Congestion Charge, and the roads outside the charge
zone were busier in the evening rush hour than those within it. RIGHTS
FREE REUTERS/Russell Boyce

RUS/JV

A couple cross a quiet four lane stretch of road at 1600GMT, where the
congestion charge zone begins at Marble Arch, London February 17, 2003.
It is the first day of the congestion charge - a fixed charge for most
motorists entering central London. Traffic in and around the capital
was lighter than expected depsite the school holidays. REUTERS/Toby
Melville.

TM/JV

A couple cross a quiet four lane stretch of road at 1600GMT, where the
congestion charge zone begins at Marble Arch, London February 17, 2003.
It is the first day of the congestion charge in London - a fixed charge
for most motorists entering central London. Traffic in and around the
capital was lighter than expected depsite the school holidays.
REUTERS/Toby Melville

TM/JV

PEDESTRIANS CROSS THE ROAD NEXT TO "C" SIGNS MARKING THE START OF THE
CONGESTION CHARGE ZONE IN CENTRAL LONDON.

A man crosses the road by a "C" sign marking the start of the
congestion charging zone in central London, February 17, 2003. The
world's biggest traffic congestion charge scheme went live at 0700 GMT
in London on Monday, using 800 cameras and 400 points in and around an
eight-square-mile (21square km) area of the city centre to monitor the
licence plates of the 250,000 motorists who drive in the area each day,
who will each pay a fee of five pounds ($8) a day. REUTERS/Russell
Boyce

RUS/ASA

A pigeon stands on a "C" sign marking the start of the congestion
charging zone in central London, February 17, 2003. The world's biggest
traffic congestion charge scheme went live at 0700 GMT in London on
Monday, using 800 cameras and 400 points in and around an
eight-square-mile (21 square km) area of the city centre to monitor the
licence plates of the 250,000 motorists who drive in the area each day,
who will each pay a fee of five pounds ($8) a day. REUTERS/Peter
Macdiarmid

ASA/CRB

A car drives over a "C" sign marking the start of the congestion
charging zone in central London, February 17, 2003. The world's biggest
traffic congestion charge scheme went live at 0700 GMT in London on
Monday, using 800 cameras and 400 points in and around an
eight-square-mile (21square km) area of the city centre to monitor the
licence plates of the 250,000 motorists who drive in the area each day,
who will each pay a fee of five pounds a day. REUTERS/Peter Macdiarmid

ASA

A cyclist passes a "C" sign indicating the start of the congestion
charging zone in central London February 17, 2003. The world's biggest
traffic congestion charge scheme went live at 0700 GMT in London on
Monday, using 800 cameras and 400 points in and around an
eight-square-mile (21square km) area of the city centre to monitor the
licence plates of the 250,000 motorists who drive in the area each day,
who will each pay a fee of five pounds a day. REUTERS/Matt Dunham

MD/ASA

A man crosses the road over a "C" sign marking the start of the
congestion charging zone in central London, February 17, 2003. The
world's biggest traffic congestion charge scheme went live at 0700 GMT
in London on Monday, using 800 cameras and 400 points in and around an
eight-square-mile (21square km) area of the city centre to monitor the
licence plates of the 250,000 motorists who drive in the area each day,
who will each pay a fee of five pounds a day. REUTERS/Russell Boyce

RUS/ASA

A woman crosses the road over a "C" sign marking the start of the
congestion charging zone in central London, February 17, 2003. The
world's biggest traffic congestion charge scheme went live at 0700 GMT
in London on Monday, using 800 cameras and 400 points in and around an
eight-square-mile (21square km) area of the city centre to monitor the
licence plates of the 250,000 motorists who drive in the area each day,
who will each pay a fee of five pounds a day. REUTERS/Russell Boyce

RUS/ASA

FOR RPA A new road sign (2L) stands amongst other traffic signs on Farringdon Road, London, January 24 2003. The 'C' letter denotes the boundary for the 'Congestion Charge' zone, where motorists will have to pay a 5 pound stirling ($8.12) fee to drive into central London starting on February 17, 2003. TPORT REUTERS/Toby Melville TM/MD

A motorcyclist passes road markings in Gower Street, London, January 24
2003. The 'C' letter denotes the boundary for the 'Congestion Charge'
zone, where motorists will have to pay a 5 pound stirling ($8.12) fee
to drive into central London starting on February 17, 2003.
REUTERS/Toby Melville

TM/MD

A TRAFFIC SIGN WITH A "C" SYMBOL INDICATING THE START OF THE CONGESTION CHARGING ZONE IS SEEN IN CENTRAL LONDON. A traffic sign with a "C" symbol indicating the start of the congestion charging zone is seen in central London February 16, 2003, the camera symbol denotes the start of the congestion CCTV (Close Circuit Television) cameras. In a Big Brother type urban surveillance scheme, 800 cameras at 400 points in and around an eight-square-mile (21 square km) chunk of the city centre will monitor the license plates of the 250,000 motorists who drive in the area every day. The new traffic scheme, which will charge motorists 5 pounds stirling ($8.10) to enter central London, will start from 0700GMT on Monday. TPORT REUTERS/Stephen Hird

A road traffic sign in Victoria, London is seen indicating the boundary of the proposed congestion zone in Westminster on February 5, 2003 ahead of it's introduction in less thantwo weeks. The 'C' letter denotes the boundary for the congestion charge zone, where motorists will have to pay a five pound stirling ($8.12) fee to drive into central London starting February 17. TPORT REUTERS/Stephen Hird SH/MD

A van drives past a road marking indicating the boundary of the
proposed congestion zone in Westminster, London on February 5, 2003
ahead of it's introduction in less than two weeks. The 'C' letter
denotes the boundary for the congestion charge zone, where motorists
will have to pay a five pounds stirling (US$8.12) fee to drive into
central London starting February 17, 2003. REUTERS/Stephen Hird

SH/MD