Responses and situations
Response	Impact on vehicle – kilometres by car	Expected in situations
		Where the system operates during limited hours such as peak time
		Where the drivers need to park outside the area or divert around it
		N/A
		Where there is potential to work, shop etc from home
		Where public transport is available and attractive and there is potential to walk or cycle
		Where modal shift and/or reduction in number of journeys is a high proportion of car journeys making owning a car uneconomic
		Where some drivers can respond by owning two cars
		Where some people may move house into the defined area to avoid the regulation

	= Weakest possible response,		= strongest possible positive response
	= Weakest possible negative response,		= strongest possible negative response

= No response

Short and long run demand responses
Demand responses in the short run may differ from those which might take place in the long run, because it takes time to decide where to live and whether or not to own a car. However, some high income car-users may consider whether or not to buy a second car with another licence number in order to drive a car everyday under implementing the number plate restrictions (Ogunsanya, 1984). The number of owned vehicles dramatically increased due to this measure in Mexico City (Goddard, 1997). Biezus et al (1999) concluded that "Numberplate circulation restriction must be considered an emergency tool to be used temporarily until other measures can be implemented to provide the required level of mobility". A system of number plate restriction needs careful experiment for confirming whether it can be an effective tool in the long run.

Permit systems

Demand responses
Responses		1st year	2-4 years	5 years	10+ years
	-
	-
	Change job location
	Shop elsewhere
	Compress working week
	Trip chain
	Work from home
	Shop from home
	Ride share
	Public transport			*	*
	Walk/cycle
	-
	-

	= Weakest possible response,		= strongest possible positive response
	= Weakest possible negative response,		= strongest possible negative response

= No response

*With regard to modal shift to public transport there may be a big shift in the short term. However, this is unlikely to increase shift in the long run if traffic congestion becomes unchanged or worse before.

Number plate restriction

Demand responses
Responses		1st year	2–4 years	5 years	10+ years
	-
	-
	Change job location
	Shop elsewhere
	Compress working week
	Trip chain
	Work from home
	Shop from home
	Ride share
	Public transport			*	*
	Walk/cycle
	-
	-

	= Weakest possible response,		= strongest possible positive response
	= Weakest possible negative response,		= strongest possible negative response

= No response

*With regard to modal shift to public transport there may be a big shift in the short term. However, this is unlikely to increase shift in the long run if traffic congestion becomes unchanged or worse before.

Level of response
As with other measures, the price elasticity of demand varies with context. The type of trip, type of traveller, price elasticity of related goods and services, and whether the elasticity accounts for short term or long term demand responses are important influential factors in the calculation and interpretation. If the permit systems are required to purchase the permission which changes the price according to the vehicles or people, the price elasticity depends on the size of the price change.

Supply impacts
There will be no increase in the supply of road space, except where regulatory restrictions include additional provision for alternatives, for example promoting public transport, providing parking lots and facilities for walking and cycling.

Financing requirements
Operating regulatory restrictions needs many enforcement staff for the checking the validity of vehicles' permits unless access control technology is used. This may particularly happen where this measure is implemented on occasional day such as air pollution emergencies or a Car-free day. Permanent permit systems impose a cost to issue permits. If the city can operate an access control technology they need only investment cost for the enforcement of the technological system.

Expected impact on key policy objectives
Regulatory restrictions are implemented to reduce traffic congestion and to develop sustainable mobility. They encourage people to reduce their overall level of car-use in the city centre by switching from car to other transport modes. Also, they will contribute to a liveable and attractive city centre. However, a large number of permits and weak enforcement will not lead to reduce traffic congestion, but to keep the original levels or increase it.

Contribution to objectives
Objective	Scale of contribution	Comment
		By reducing delays and improving reliability. Contribution may be greater where promotion is accompanied by park and ride or an improvement in public transport service levels
		By improving streetscape and by reducing community severance; but outside of a defined area may be worse because of diverted traffic
		By reducing air and noise pollution and pressures on green space and environmentally sensitive sites; but outside of a defined area may be worse because of diverted traffic
		By improving public transport conditions; but there are often many exemptions based on unclear justification, making it an inequitable measure.
		By reducing traffic levels
		By freeing up potentially productive time currently lost in congestion and by enabling freight operators to rationalize their fleet operations
		By operating costs for checking the validity of permits, but a fine from violated vehicles of the traffic regulation may be used as substantial amounts of revenue.

	= Weakest possible positive contribution,		= strongest possible positive contribution
	= Weakest possible negative contribution		= strongest possible negative contribution

= No contribution

Expected impact on problems
Regulatory restrictions would reduce car use in the defined area, hence they have the potential to contribute to the alleviation of a number of key problems.

Contribution to alleviation of key problems
Problem	Scale of contribution	Comment
Congestion-related delay		By reducing traffic volumes in a defined area, but by increasing diverted traffic outside an area
Congestion-related unreliability		By reducing traffic volumes in a defined area, but by increasing diverted traffic outside an area
Community severance		By reducing traffic volumes in a defined area, but by increasing diverted traffic outside an area
Visual intrusion		By reducing traffic volumes in a defined area, but by increasing diverted traffic outside an area
Lack of amenity		Where increased walking and cycling results from permanent ban of most vehicles in a city centre there may be an enhancement of the viability of local facilities
Global warming		By reducing traffic-related CO2 emissions
Local air pollution		By reducing emissions of NOx, particulates and other local pollutants, but increasing emissions outside an area from diverted traffic
Noise		By reducing traffic volumes in a defined area, but by increasing the diverted traffic outside an area
Reduction of green space		By reducing pressure for new road building and city expansion
Damage to environmentally sensitive sites		By reducing traffic volumes
Poor accessibility for those without a car and those with mobility impairments		By enhancing the reliability of public transport and by discouraging car-oriented development in a city centre
Disproportionate disadvantaging of particular social or geographic groups		By enhancing the reliability of public transport and reducing traffic levels in a defined area
Number, severity and risk of accidents		By reducing traffic volumes in a defined area, but by increasing diverted traffic outside an area
Suppression of the potential for economic activity in the area		By improving the efficiency of the local road network through reduced congestion

	= Weakest possible positive contribution,		= strongest possible positive contribution
	= Weakest possible negative contribution		= strongest possible negative contribution

= No contribution

Expected winners and losers
One would not expect everybody to benefit equally from any transport measure. Indeed, those who are exempted from restrictions should benefit from reduced congestion. However, there can be many winners if effective measures of public transport and parking management are included as part of a package.

Winners and losers
Group	Scale of contribution	Comment
Large scale freight and commercial traffic		High value journeys - less time spent in congestion the greater the vehicle utilization - relatively small proportion of journey distance in urban conditions. In addition, usually exempted from restrictions.
Small businesses		Where these are local and reduced car use encourages use of local amenities. However, where prohibited from entering may become less attractive in city centre.
High income car-users		High income associated with high value of time and thus continued car use for high value journeys by sometime purchasing a second car or permitted car. These journeys will benefit from reduced congestion.
People with a low income		Where prohibited or restricted entering their vehicles into the city centre. This may benefit from reduced congestion, but not solve problems associated with low income car users.
People with poor access to public transport		Reduced congestion will improve public transport reliability, but not solve problems associated with poor access for public transport users.
All existing public transport users		Reduced congestion will improve public transport reliability. In addition, where increased demand for alternatives results in increased quality and volume of service.
People living adjacent to the area target		Where prohibited or restricted entering their vehicles into the city centre and increasing in diverted traffic on the peripheral area.
People making high value, important journeys		These journeys will have higher values of time and may continue to be made by car and usually be exempted from restrictions.
The average car users		Where they may benefit from reduced congestion.

	= weakest possible benefit,		= strongest benefit
	= weakest possible disbenefet,		= strongest possible disbenefit

= neither wins nor loses

Barriers to implementation

Scale of barriers
Barrier	Scale	Comment
Legal		As regulatory restrictions are usually based on the road traffic laws or the air pollution control laws, there are no barriers to implementation. However we need to ensure the right of mobility among those who own a private car.
Finance		If permit systems implemented as permanent measures, checking systems such as a tollgates are required.
Political		The car users in commuting or businesses, usually not exempted from restriction, are likely to oppose regulatory restrictions and therefore they might be politically unacceptable.
Feasibility		Acceptance of public and cooperation of relative institutions is the key feasibility issue.

= minimal barrier,

= most significant barrier