Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: On a discrete optimal velocity model and its continuous and
  ultradiscrete relatives   We propose a discrete traffic flow model with discrete time. Continuum limit
of this model is equivalent to the optimal velocity model. It has also an
ultradiscrete limit and a piecewise-linear type of traffic flow model is
obtained. Both models show phase transition from free flow to jam in a
fundamental diagram. Moreover, the ultradiscrete model includes the
Fukui-Ishibashi model in a special case.

13
The categories of this paper are: quant-ph
32
The categories of this paper are: atom-ph
10
The categories of this paper are: q-bio
19
The categories of this paper are: eess
33
The categories of this paper are: plasm-ph
3
The categories of this paper are: physics
11
The categories of this paper are: hep-lat
8
The categories of this paper are: hep-ex
30
The categories of this paper are: q-alg
37
The categories of this paper are: supr-con
5
The categories of this paper are: gr-qc
26
The categories of this paper are: bayes-an
31
The categories of this paper are: ao-sci
20
The categories of this paper are: acc-phys
17
The categories of this paper are: q-fin
15
The categories of this paper are: nucl-ex