Fundamental diagram of traffic flow

The fundamental diagram of traffic flow is a diagram that gives a relation between the traffic flux and the traffic density. A macroscopic traffic model involving traffic flux, traffic density and velocity forms the basis of the fundamental diagram, it can be used to predict the capability of a road system, or its behaviour when applying inflow regulation or speed limits. There is a connection between traffic density and vehicle velocity: The more vehicles are on a road, the slower their velocity will be. To prevent congestion and to keep traffic flow stable, the number of vehicles entering the control zone has to be smaller or equal to the number of vehicles leaving the zone in the same time. At a critical traffic density and a corresponding critical velocity the state of flow will change from stable to unstable. If one of the vehicles brakes in unstable flow regime the flow will collapse; the primary tool for graphically displaying information in the study traffic flow is the fundamental diagram.

Fundamental diagrams consist of three different graphs: flow-density, speed-flow, speed-density. The graphs are two dimensional graphs. All the graphs are related by the equation “flow = speed * density”; the fundamental diagrams were derived by the plotting of field data points and giving these data points a best fit curve. With the fundamental diagrams researchers can explore the relationship between speed and density of traffic; the speed-density relationship is linear with a negative slope. The line crosses the speed axis, y, at the free flow speed, the line crosses the density axis, x, at the jam density. Here the speed approaches free flow speed; as the density increases, the speed of the vehicles on the roadway decreases. The speed reaches zero when the density equals the jam density. In the study of traffic flow theory, the flow-density diagram is used to determine the traffic state of a roadway. There are two types of flow density graphs: parabolic and triangular. Academia views the triangular flow-density curve as more the accurate representation of real world events.

The triangular curve consists of two vectors. The first vector is the freeflow side of the curve; this vector is created by placing the freeflow velocity vector of a roadway at the origin of the flow-density graph. The second vector is the congested branch, created by placing the vector of the shock wave speed at zero flow and jam density; the congested branch has a negative slope, which implies that the higher the density on the congested branch the lower the flow. The intersection of freeflow and congested vectors is the apex of the curve and is considered the capacity of the roadway, the traffic condition at which the maximum number of vehicles can pass by a point in a given time period; the flow and capacity at which this point occurs is the optimum flow and optimum density, respectively. The flow density diagram is used to give the traffic condition of a roadway. With the traffic conditions, time-space diagrams can be created to give travel time and queue lengths of a road segment. Speed – flow diagrams are used to determine the speed at which the optimum flow occurs.

There are two shapes of the speed-flow curve. The speed-flow curve consists of two branches, the free flow and congested branches; the diagram is not a function, allowing the flow variable to exist at two different speeds. The flow variable existing at two different speeds occurs when the speed is higher and the density is lower or when the speed is lower and the density is higher, which allows for the same flow rate. In the first speed-flow diagram, the free flow branch is a horizontal line, which shows that the roadway is at free flow speed until the optimum flow is reached. Once the optimum flow is reached, the diagram switches to the congested branch, a parabolic shape; the second speed flow diagram is a parabola. The parabola suggests that the only time there is free flow speed is when the density approaches zero; this parabolic graph contains an optimum flow. The optimum flow divides the free flow and congested branches on the parabolic graph. A macroscopic fundamental diagram is type of traffic flow fundamental diagram that relates space-mean flow and speed of an entire network with n number of links as shown in Figure 1.

The MFD thus represents the capacity, μ, of the network in terms of vehicle density with μ 1 being the maximum capacity of the network and η being the jam density of the network. The maximum capacity or “sweet spot” of the network is the region at the peak of the MFD function; the space-mean flow, q ¯, across all the links of a given network can be expressed by: q ¯ = ∑ k = 1 n d i n T L, where B is the area in the time-space diagram shown in Figure 2. The space-mean density, k ¯, across al

Pejman Bazeghi

Pejman Bazeghi is an Iranian actor. Bazeghi was born on August 1974 in Tehran, Iran to an ethnic Persian family, he is the second child of a family of five, with an origin from the Northern part of Lahijan. During his childhood, due to his father’s job, he moved and lived in different cities which gave him a lot of experience for his future. After the Islamic revolution, when he was only four years old, his family moved to Rasht. During Iran’s war with Iraq because his father became one of the guardians to defend southern sea borders of Iran, his family moved to Boushehr. After the war and his family’s return to Tehran, Pejman got accepted in the Islamic Azad University, Lahijan Branch and moved there to continue his education in the field of Mining engineering, it was there he got interested in acting. In 1994, he entered the central youth cinema of Gilan and acted in his first film called Eteraf, directed by Majid fahimkhah. After that, he acted in his first television series, Azhanse Doosti, for about two years, where he got the chance of working alongside Hossein Panahi.

He became a more prominent actor in 2004 after starring in the film Duel, which won six awards at the 22nd Fajr International Film Festival. Films: The Confession The Young Puberty The Girl In The Cage The Friday’s Soldiers Tara and Strawberry Fever Duel Cafe Setare Death Is My Profession Nadarha Nahid Old Flame Blade and Termeh Symphony No. 9 2019TV Series: Paytakht directed by Siroos Moghaddam in 2012 Friendly Agency directed by Ahmad Ramezanzadeh This is Not a Court directed by Asghar Tavasoli The Elite Group directed by Mehrdad Khoshbakht Under The City’s Sky directed by Mehran Ghafourian The Lost directed by Rambod Javan The Sea People directed by Syrouse Moghadam The Passing of Love directed by Mohamadreza Ahan The Edge of Darkness Mard-e Hezar-Chehreh directed by Mehran Modiri in 2008 Marde Do Hezar Chehreh directed by Mehran Modiri in 2009 Gando directed by Javad Afsha in 2019 Iranian cinema Pejman Bazeghi on Instagram Pejman Bazeghi on IMDb