Patterns & Metaphors
Traffic regulation
Template:
The movement of traffic of different kinds, of different densities, at different speeds and with different directions, especially in an urban environment, is (self-) regulated by a range of techniques. These include: basic road rules (driving on right or left), prohibited actions (no entry, speed limit, no stopping, no waiting, no parking), required actions (stop, keep left, yield, turn right), limited access (no cyclists), and special warnings (dangerous crossing, etc). To improve traffic flow, traffic signals may be used permitting an orderly alternation in direction of movement. These may be phased in various ways to improve flow in an area (e.g. green phasing for a group of vehicles moving at constant speed along a route through the area), although area traffic control responsive to a range of traffic conditions must optimize flows by compassing current conditions to models based on past experience. Traffic of different types may also be segregated: pedestrian from vehicles, local from long-distance traffic (e.g. on expressways with merging lanes and cloverleaf junctions).
Metaphor:
The progress of groups of different kinds, at different rates and with conflicting policies, especially in complex social environments, could be regulated by a range of techniques. A cycle of signals may be used to enable groups with conflicting policies to progress during alternate periods. Actions of groups of different types may be segregated. The progress of groups with conflicting but interrelated policies may be facilitated by devising means for such policies to merge into each other rather than cut across each other.
[Features] The precision with which a wide range of potential conflict situations must be handled using a minimum set of rules comprehensible to all concerned. The explicit recognition that priority is given to each according to particular circumstances. The manner in which traffic under many conditions controls itself when each vehicle recognizes under what conditions it has right of way or must give way.
[Contrast] Under certain conference and air-time rules, groups are given start/stop priority, over each other in succession in order to express their viewpoints. The alternation of political parties in power may be considered in this light; as election being the process through which a decision is taken on the traffic signals. But in general, present policy control in this metaphor can be compared to a procession (or 'progress') in one direction with the support of security forces which ensure that all access roads be blocked off and all opposing traffic suppressed. When the procession has petered out, another such 'convoy' may be organized in another direction to cater for the traffic stream blocked by the first. This corresponds to a very primitive traffic control approach. It takes no account of the sophisticated blend of control and delegation of responsibility to drivers which is characteristic of modern traffic patterns.
[Keys] Basic road rule (driving on right or left) and the history of its emergence. Collision avoidance. Co-presence of different developmental stages of traffic management (stop streets, one-way streets, round-abouts, filtering systems, underpasses and cloverleaf intersections). Public and private vehicles. Traffic policemen. Sophisticated area control systems to adjust to congestion, peak periods, and emergencies.<
