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Table 2 List of variables used in this paper
From: Modelling delay saving through pro-active incident management techniques
Symbol | Definition | Units | Notes |
|---|---|---|---|
m,n | Number of lanes | Available or normal number of lanes according to context | |
μ | Lane capacity | PCU/ha | Normal capacity of one lane for flowing traffic |
q | Flow | veh/h | May be subscripted corresponding to sections in Fig. 2 |
ρ | Density | veh/km | k is also commonly used |
v | Speed | km/h | Strictly space-mean, though time-mean is often measuredb |
V f | Free-flow speed | km/h | Maximum speed with no other traffic |
ρ c | Critical density | veh/km | Point at which flow breaks down and congestion starts |
v c | Critical speed | km/h | Corresponding to critical density |
ρ max | Jam density | veh/km | Notional density at which speed is zero (k j sometimes used) |
α | Speed/flow slope | km/veh | Determines how speed decreases with flow if uncongested |
λ | Jam spacing | m | Effective minimum road space required by vehicle |
τ | Response time | sec | Effective reaction and response time of driver |
w,w f | Wave speed | km/h | Speed at which a disturbance propagates upstream |
β,γ,χ | Capacity factors | Parameters used to adjust lane capacities for calibration | |
δ i | Diversion factors | Diversion could vary with time (not used in modelling) | |
v ij | Wave speeds | km/h | Speeds of propagation of state boundaries in queue |
r i | Queue reach | km | Upstream position of tail of queue at various times |
t i | Event times | h | Times at which traffic or queue state changes |
X | Max. queue extent | km | Maximum length of queue, head to tail |
R | Max. queue reach | km | Maximum distance of queue tail from incident site |
S i | Time-space ‘area’ | km-h | Measure of amount of queuing in a given period |
D | Total delay | veh-h | Allows for time that would have been taken at free-flow |