Traffic Grammar and Algorithmic Complexity in Urban Freeway Flow Patterns Kingsley E. Haynes & Rajendra Kulkarni & Roger Stough Published online: 5 September 2007 # Springer Science + Business Media, LLC 2007 Abstract This paper uses techniques from formal language theory to describe the linear spatial patterns in urban freeway traffic flows in order to understand and analyze “hidden order” in such high volume systems. A method for measuring randomness based on algorithmic entropy is introduced and developed. These concepts are oper- ationalized using Pincus’ approximate entropy formulation in an appropriate illustration. These measures, which may be viewed as counterintuitive, are believed to offer robust and rigorous guidance to enhance the overall understanding of efficiency in urban freeway traffic systems. Utilization of such measures should be facilitated by information generated by real time intelligent transportation systems (ITS) technologies and may prove helpful in real time traffic flow management. Keywords Formal language theory . Algorithmic complexity . Intelligent transportation systems (ITS) . Approximate entropy Netw Spat Econ (2007) 7:333–351 DOI 10.1007/s11067-007-9032-9 An earlier version of this paper was presented at the Fifth Joint Conference on Computing and Information Sciences, February 2000, Atlantic City, NJ. The authors appreciate the support of the NSF/ EPA Grant #SES-9976483 “Social Vulnerability Analysis and NSF Grant #ECS-0085981 “Road Transportation as a Complex Adaptive System” as well as the School of Public Policy’ s USDOT Center of Excellence in Evaluation and Implementation funded under DOT Grant #DTRS98-G-0013. Any errors are the responsibility of the authors. K. E. Haynes (*) : R. Kulkarni : R. Stough School of Public Policy, George Mason University, Fairfax, VA 22030, USA e-mail: khaynes@gmu.edu R. Kulkarni e-mail: rkulkarn@gmu.edu R. Stough e-mail: rstough@gmu.edu R. Stough George Mason University, Fairfax, VA 22030, USA