TRN-31

Traffic flow q = k v

q = k v. The definition of flow on a homogeneous stream.

Reading speed

Trafficq = k v

Governing equation

q=kv

where

k: Density (veh/km)
v: Space-mean speed (km/h)
q: Flow (veh/h)

Lecture brief

Historical brief

Highway and traffic theory crystallized with Greenshields’ 1935 speed–density line, then AASHTO stopping sight and equivalent axles. The lab is that operational arithmetic of flow, braking and pavement load. This sheet (TRN-31 — Traffic flow q = k v) is the form associated with q = k v. Working symbols: $k$ , $v$ $\rightarrow$ $q$ . Vehicles passing a point per hour equal density times space-mean speed. The fundamental identity.

Purpose

Purpose: compute

q

from

k

v

in Transport via

q=kv

q = k v. The definition of flow on a homogeneous stream. Use it when a real transport question must be answered in SI before a code check.

Live realistic example

In symbols

Live case. Given

k = 25.000\,\mathrm{veh/km}

v = 80.000\,\mathrm{km/h}

, the governing relation

q=kv

yields

q = 2000\,\mathrm{veh/h}

. A density, a speed, a flow. Move a slider: the numbers are this situation, not a canned story.

Calculator

Inputs

Density k25 veh/kmSpace-mean speed v80 km/h

Outputs

Flow q2000 veh/h

Reading speed

Watch on YouTube

Free library

Full library

Free PDF / open book

YouTube channels

00:0 / 00:08

Narration of this film

A density, a speed, a flow.

Vehicles passing a point per hour equal density times space-mean speed. The fundamental identity.

Reading speed

Watch on YouTube