Imagine if you were being charged tens of dollars to drive into the center of your home city each day.

Around Europe, many drivers already face such a charge. London is one such city, and residents have been paying to enter the center of the capital since 2003.

Low-emission vehicles have commonly been exempt--but new plans being drawn up by Transport for London (TfL) could change that later this year.

So what is it?

Called the Congestion Charge, London's scheme is little more than a vehicle tax. Its real purpose isn't to ease congestion, but rather reduce pollution in the city by discouraging drivers from driving within the zone.

Currently, the charge to enter London is just under $16 per day, meaning those who regularly need to travel into the center, and don't use London's buses, taxis or tube, can pay thousands of dollars per year.

Several models currently on sale in the UK are exempt from the charge, which doesn't apply to vehicles emitting under 100 grams per kilometer of carbon dioxide.

Proposed changes

Transport for London is currently asking residents to submit their views on proposed changes to the existing system.

These changes include a drop of the exemption limit, from 100 g/m CO2 down to just 75 g/km. That effectively rules out exemption for everything except plug-in vehicles--a Toyota Prius emits 89 g/km under European fuel efficiency testing. The cleanest non-plugin car currently on sale, the Toyota Yaris Hybrid, puts out only 79 g/km, just missing the new target.

Plug-in cars, on the other hand, comfortably dip under the limit. A plug-in Prius is rated at only 49 g/km, a Chevy Volt just 27 g/km.

Mixed messages

On the face of it, encouraging people into ever-greener vehicles is a good thing. However, the proposed limit fails to take account of certain factors.

The first is that, under the old system, thousands of drivers moved into cleaner, better-mpg cars in order to benefit from the fee exemption. Many of these were quite accessible in terms of cost, where many plug-ins are not.

With the sub-100 g/km cars no longer incentivised, and plug-ins out of reach for many, there's little to stop drivers making their next car a less efficient one. If they can't benefit from charge exemption, it doesn't really matter whether the car they subsequently choose gets 76 g/km or over 100.

As some consolation, owners of existing sub-100 g/km cars would get an extra two years of exemption--but after that, they'd pay the same $16 as everyone else.

Cutting diesel pollution

TfL says its plans are aimed at cutting diesel pollution, as low-CO2 diesels have become increasingly common on London's roads, thanks to the incentives.

It states that a Euro 4-standard diesel emits 22 times the particulate matter of the typical gasoline car--neglecting to mention that currently, exempt diesels must meet Euro 5 standards, which are five times cleaner.

That's in contrast to the taxis and buses responsible for pumping out tonnes of diesel particulate matter into London's air, doing far more damage than cars, which get cleaner every year.

The typical London black cab only has to meet Euro 3 standards--twice the particulate matter of Euro 4, ten times that of Euro 5, and over forty times that of a Euro 5 gasoline vehicle. They also emit vastly more nitrogen oxides--a large cause of smog.

These vehicles also spend all day on London's roads, rather than the few hours of the typical car, which remains parked for most of the day.

Plug-in rules

TfL has laid down a list of criteria a vehicle would have to meet in order to be exempt. The good news is that pure-electric vehicles would be automatically exempt.

Plug-in hybrid vehicles would need to emit below 75 g/km of CO2, and have an all-electric range of greater than 10 miles. That means cars like the Prius Plug-In, with its 15-mile European EV range, will remain exempt.

While many will undoubtedly welcome London's plans to become a cleaner city--it's currently one of the most polluted in Europe--disincentivizing some of the existing cleaner vehicles seems like a step backwards.

Surely, it would make more sense to try and dissuade some of the more polluting vehicles from entering, or invest more heavily in cleaner, range-extended and hybrid buses and taxis?

What are your thoughts on London's proposed Congestion Charge rules? Do you think it's for the greater good, or is it simply a kick in the teeth to all those who've already made the effort to buy greener vehicles?


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