Taxonomy and description
Types of Regulatory Restrictions
Permit systems operate to ban certain types of traffic
from entering a defined area during specific time periods by the issue
of permits. Usually private vehicles from outside the area and through
traffic are discouraged, whilst residents' vehicles within the area and
service and commercial vehicles are usually exempted from restrictions
since they can be justified to be essential in a city centre. The category
of vehicles and people who qualify for such exemptions are determined
by local or municipal authorities.
Number plate restrictions are usually operated as the odds and evens system, in which vehicles with odd number plates and those with even number plates are admitted on alternate days determined by a day of the week or date. The system in Sao Paulo is based on the last digit of the number plate, where for example the vehicles prohibited from driving on Monday are those whose number plates have as their last digits either 1 or 2. Some categories of vehicles and people are also exempted in number plate restrictions.
Both types are implemented not only regularly but also temporarily. The regular measures are usually operated either weekday or weekend or everyday. The temporary measures are implemented on days in excess of threshold of an air pollution level, or for specific events such as a Car-free day. Number plate restrictions are usually used for the temporary measures because they are easier to enforce than permit systems. Hours of enforcement are usually working hours (e.g. 9:00 a.m. to 5:00 p.m.), but sometimes are only morning and evening peak hours.
An applicable access control technology was developed in the 1990s and operated in some European cities. Drivers who have a permit can pass the toll without stopping. There are a number of options for technologies (Miles et al, 1998):
Video-based systems - Optical Character Recognition (OCR)
and a permitted list. Use of number plate recognition requires suitable
camera positions to provide number plate visibility and adequate lighting.
For example, the number plate of a car following close behind a large
vehicle may never be in the direct view of the camera.
A magnetic or smart card pass that has to be manually inserted by the driver into a slot or through a contactless reader is a cheap but slow option.
A barcode sticker and reader located at the side of the
road uses established technology, but is likely to be slow.