85th Percentile Speed

This is the speed up to which 85% of the traffic is measured as travelling on a particular road in a particular direction using a speed gun or pneumatic tubes. It is a parameter used to consider the geometry of a road, like the safe level of forward visibility along a road and the appropriate visibility splays either side of a junction or planned access road. It is accepted that 15% of the traffic will be travelling faster than this speed.

ATC [Automatic Traffic Count]

These can be conducted by placing hydraulic tubes across the road, often for periods of one week or more, to record the number of vehicles travelling in each direction. The ATC can record vehicles in up to 13 categories and also record vehicle speed at the same time.

CPZ [Controlled Parking Zone]

A CPZ is an area where parking is controlled. Some limited parking may be allowed for short time periods. In general the parking is restricted to local residents with permits. Times of the zone will be displayed on the zone entry signs, which will be present on all routes in the zone.

Cycle Time

At a signalised junction the cycle time is the period required for all approaches at the signals to run. This is measured as the time which elapses between the start of an approach and the point at which that particular approach starts again. Typically a cycle time may be up to a maximum of 120 seconds.

Degree of Saturation [DoS] - Saturation Flow Survey

This is the ratio of the actual traffic flow to the maximum flow, and indicates how much demand a lane or lanes can take or approach is experiencing compared to its total capacity. A Dos of 90% on an approach to signals indicates that it is approaching its theoretical capacity, and values of 100% indicates it has exceeded its absolute capacity.

Furness Method

Some competitors may profess to use "mathematical models" (such as 'Furness' etc.) to "count" a roundabout - whilst others will not declare this fact, but use the method in any case. It will be shown further below that no such "count" is actually possible using a mathematical model.

Lambeth Methodology

Some competitors may profess to use "mathematical models" (such as 'Furness' etc.) to "count" a roundabout - whilst others will not declare this fact, but use the method in any case. It will be shown further below that no such "count" is actually possible using a mathematical model.

Highways Agency

The HA is responsible for the Strategic Road Network [SRN] and has the power to direct a refusal of planning application which it believes would adversely affect the operation or safety of an SRN.

LTP [Local Transport Plan]

An LTP is a plan produced by strategic transport authorities i.e. County and Local Councils, Transport authorities. It should provide advice to the local planning authority on highway and transport matters. It is a forward looking plan with set objectives to cover pollution, accessibility and transport and is typically carried to cover a number of years [typically 5 years]. The information is then presented to the Dft [Department of Transport]. It can then be used when a local planning authority or the Secretary of State determines a planning application.

Mean Max Queue - Queue Length Survey

The mean maximum queue measured in PCU [Passenger Car Unit] is an approximate average of the maximum queues likely to be encountered at junction in a modelled network.

Pedestrian Crossings

1] Pelican Crossing

Features a set of traffic lights with a push button and two coloured lamps for pedestrians using the crossing. The “Green Man” shown to pedestrians is on the other side of the road. The “Green Man” is followed by a “Flashing Green Man/Flashing Amber” which gives some flexibility to the movement of pedestrians and traffic.

2] Puffin Crossing

Differs from a pelican crossing in that the lights controlling the pedestrians are on the near side of the road in such a position that makes the pedestrian face towards the closest lane of oncoming traffic.

3] Pegasus Crossing

Like a toucan crossing but for horses. Where a bridleway crosses a main road.

The push buttons are located 2m from the ground and the green man is replaced by a green horse.

4] Toucan Crossing

A combined pedestrian/cycle crossing that allows bicycles to be ridden across. There is a cycle and pedestrian green signal and it is suggested that the name derives because “two can” cross at the same time! The signal lights may be near side or on the opposite side of the road.

5] Zebra Crossing

Alternating longitudinal black and white stripes on the road [hence named after the Zebra] running parallel to the traffic flow.

PIA [Personal Injury Accident]

These are accidents which involve personal injury to a driver or other road users.

Transport Assessment [TA]

Where a new development is likely to have significant transport implications, a Transport Assessment [TA] should be prepared and submitted with a planning application for the development.

Travel Plan [TP]

A TP accompanies a Transport Assessment and is aimed at reducing the reliance on private car use over time.

TRICS [Trip Rate Information Computer System]

It is the only national trip generation and analysis database and contains trip generation and site information for over 2800 sites and numerous land uses.

Visibility Splay

A visibility Splay is a diagram indicating the area adjacent to a road junction or access which should be free from obstruction to motorists and pedestrians. There are varying standards for visibility splays depending on the speed of vehicle traffic on the roads.