T-Charge stands for Toxicity Charge and is being introduced on the 23rd October 2017 as an addition to the Congestion Charge to discourage drivers of older, dirtier vehicles (registered before 2006) from driving into London. This isn't the same as the ULEZ Zone which will start around 2019/2020.
London residents were given the opportunity to take part in a consultation process online to get an idea of what they thought about the new T-Charge and how they thought it should operate. Apparently most Londoners thought there should be an additional charge to discourage the more polluting vehicles driving in the centre of London.
The T-Charge applies to both diesel and petrol vehicles registered before 2006 and will put an additional £10 on top of the existing Congestion Charge fee - so some vehicles will be charged £21.50 to enter central London. Vehicles included in this are cars, vans, minibuses, buses, coaches, HGVs, motorised caravans, breakdown vehicles, private ambulances, etc.
The good news is that Motorcycles are not subject to the T-Charge. For Trikes, only those that are currently subject to the Congestion Charge and registered before 2006 will need to pay the T-Charge.
While it's good that Motorcycles aren't being surcharged, it was really an easy decision to make for TfL as they were already not being charged for the Congestion Zone. There is still the ULEZ zone hanging over our heads with a Motorcycle-discouraging charge at the same level as cars when Motorcycles account for less than 1% of the congestion and pollution. There will be a further consultation on that later this year and hopefully we can get Motorcycles to either be exempt from that too or to pay a lower charge than cars do to promote their use as congestion busting vehicles.