The majority of motorists driving into the downtown area of England's capital were hit on Monday with a doubled toll. A new Ultra Low Emission Zone (ULEZ) tax took effect, which, combined with the existing congestion tax, raised the total amount drivers must pay to enter the city center during working hours to £24 (US $31.30).

The ULEZ tax represents a massive expansion of the tolling concept. It is collected in addition to the congestion charge that only applies from 7am to 6pm. The £12.50 ULEZ tax (US $16.30), by contrast, is collected around a clock that resets at midnight. A driver who drives into the zone a few minutes before minute and then leaves a few minutes afterward must pay two charges for a total of £25 (US $32.60). While the ULEZ boundaries are the same as those for the congestion tax right now, the ULEZ tax will grow to cover all of greater London by 2021.

Mayor Sadiq Khan introduced the ULEZ charge as a way of encouraging drivers to abandon their current vehicles for electric-powered alternatives that are currently favored by city officials. Taxis, favored by the government, are exempt from the tax while Uber drivers must pay the full charge.

At present, gasoline-powered cars that do not meet the Euro 4 regulations -- in general, this means cars made before 2006 -- must pay. Most diesels made before 2015 will not meet the Euro 6 standard needed to escape the charge. The Alliance of British Drivers (ABD) slammed this arrangement as fundamentally unfair.

"Those who bought diesel vehicles only a few years ago, encouraged by the government because of their lower CO2 emissions, will now find they are paying this tax or will have to buy a new vehicle," the group explained. "There are numerous anomalies in this tax which will particularly affect those who drive older cars who are typically the poorer members of the community. Those who drive very expensive modern supercars or luxury vehicles with large engines will not be paying even though the emissions from them are high."

Transport for London has installed a massive network of license plate reading cameras to enforce the tax. Drivers who fail to pay within 24 hours of traveling in a zone will be hit with a £160 (US $209) penalty for each unpaid day of driving in the zone.