Far from being anti-motorist, 20 mph limits give taxi and private hire vehicle drivers many benefits including extra potential customers
Taxi drivers benefit when authorities adopt community-wide default 20 mph limits without humps. Some roads have higher speeds where merited. Importantly, more adults will feel able to manage without owning a private car, thereby increasing sustainable transport options including car sharing and taxi use. Advantages include:
More potential taxi users as owning a car becomes less essential and options other than driving oneself are safer, more attractive and affordable. This raises taxi incomes.
Taxi Passengers Benefit. Many taxi trips start and end with a short walk. 20mph speed limits make it safer, easier and more pleasant for taxi users, particularly older people and the less mobile, to get to and from a rank.
Little effect on journey times except increased reliability. Most taxis spend very little time travelling over 20 mph in residential areas. Average trips take less than 40 seconds extra. Fewer unnecessary car trips frees up road space. Journey times are more reliable. Scheduling of taxi jobs is easier and customers enjoy better service.
Fewer injured car users. Overall there were 22% fewer casualties in Portsmouth: drivers had 23% fewer and passengers 31% fewer after 2 years of wide area 20 mph limits. Elderly drivers had 50% fewer injuries and 40% fewer injured passengers.
Fuel use, CO2 and costs fall 12%. German 30km/h (18.6 mph) zones led to car drivers changing gear 12% less often, braking 14% less often and using 12% less fuel.
Less Congestion. At 20 mph more cars occupy the same road space due shorter gaps between each relative to 30 mph, easing traffic ‘flow’. Junctions are more efficient as drivers can merge into shorter gaps. Less risk encourages sustainable travel and shared transport.
Cleaner air quality especially helps professional drivers who breathe in-car air which is three times more polluted than at the pavement. Standing traffic, which produces unnecessary fumes, reduces as traffic flow smooths. Less fuel is burnt due to less acceleration and the transfer of some trips away from private cars to other modes like taxis.
Motoring costs drop from less brake and tyre wear. As crashes fall, so also do legal and repair bills. Motor insurance premiums could lower in 20 mph limit post codes.
Driving becomes a pleasanter occupation. Stress reduces as drivers have more time to react to hazards. Fewer road rage incidents occur due to more considerate driving styles, including less overtaking and it is easier to pull out. With casualties down by 22% some drivers will suffer less anxiety from their part in liability for crashes. Noise also reduces and there are fewer potholes.
Total 20 involves signage only, not speed bumps
 DfT. Interim Evaluation of the Implementation of 20 mph Speed Limits in Portsmouth Final Report - Sep 2010
 An illustrated guide to traffic calming. by Dr Carmen Hass-Klau (1990)
 Environmental Transport Association. Road User Exposure To Air Pollution Nov 1997