aldous
Jul2-08, 07:30 AM
Hello,
I'm a computer science student in desperate need for help. In the process of writing my master's thesis I've successfully developed a traffic simulation using a model I've found in the traffic research literature, the IDM, to be precise. This model seems straight-forward and is easy to grasp even for a dim mind like mine.
However, I fail to understand older car following models, such as presented by Jiménez et al. (2000) (http://www-sop.inria.fr/mascotte/Philippe.Mussi/papers/esm2000.ps) and
Treiber et al. (2000) (http://arxiv.org/PS_cache/cond-mat/pdf/0002/0002177v2.pdf)... Hopefully just because I simply don't know what some variables mean, which are apparently not introduced.
Jiménez et al. (2000) state that all car following models can be summarized by:
\ddot{x}_f ( t+T_r ) = \lambda * [ \dot{x}_{l}(t) - \dot{x}_{f}(t)] \quad (1)
\lambda = \frac{a_{l,m}* \dot{x}_{f}^m(t+T)}{[x_{l}(t)-x_{f}(t)]^l} \quad (2)
So my questions: what does \dot{x}_f^m express? Sure, \dot{x}_f is the velocity of vehicle f, but what is m? The vehicle's mass? Why would one want to potentiate the velocity by the mass? I'm lost! Further, I interpreted l -- being used as an index in equation 1 -- as the leading car, f denoting the following car. However, in equation 2, l is used as a power? How is this to be interpreted?
Similarly, Treiber et al. (2000) state that older car following models can be reduced to that formula:
\dot{v}_\alpha ( t+T_r ) = \frac{-\lambda v_\alpha^m \Delta v_\alpha}{s_\alpha^l} \quad (3)
My question: the \lambda in eq. 3 seems to be different to the \lambda in eq. 2. Is it this a variable often used in physics one should just know? (It is not defined in the paper)
Thank you very much in advance for any pointers!
Alexander
I'm a computer science student in desperate need for help. In the process of writing my master's thesis I've successfully developed a traffic simulation using a model I've found in the traffic research literature, the IDM, to be precise. This model seems straight-forward and is easy to grasp even for a dim mind like mine.
However, I fail to understand older car following models, such as presented by Jiménez et al. (2000) (http://www-sop.inria.fr/mascotte/Philippe.Mussi/papers/esm2000.ps) and
Treiber et al. (2000) (http://arxiv.org/PS_cache/cond-mat/pdf/0002/0002177v2.pdf)... Hopefully just because I simply don't know what some variables mean, which are apparently not introduced.
Jiménez et al. (2000) state that all car following models can be summarized by:
\ddot{x}_f ( t+T_r ) = \lambda * [ \dot{x}_{l}(t) - \dot{x}_{f}(t)] \quad (1)
\lambda = \frac{a_{l,m}* \dot{x}_{f}^m(t+T)}{[x_{l}(t)-x_{f}(t)]^l} \quad (2)
So my questions: what does \dot{x}_f^m express? Sure, \dot{x}_f is the velocity of vehicle f, but what is m? The vehicle's mass? Why would one want to potentiate the velocity by the mass? I'm lost! Further, I interpreted l -- being used as an index in equation 1 -- as the leading car, f denoting the following car. However, in equation 2, l is used as a power? How is this to be interpreted?
Similarly, Treiber et al. (2000) state that older car following models can be reduced to that formula:
\dot{v}_\alpha ( t+T_r ) = \frac{-\lambda v_\alpha^m \Delta v_\alpha}{s_\alpha^l} \quad (3)
My question: the \lambda in eq. 3 seems to be different to the \lambda in eq. 2. Is it this a variable often used in physics one should just know? (It is not defined in the paper)
Thank you very much in advance for any pointers!
Alexander