This paper presents results from a travel survey of downtown area employees conducted during the 1984 Los Angeles Summer Olympics. The Olympics provided a unique opportunity to observe travel demand responses to major anticipated changes in the level of service of the transportation system. 

The survey examined all aspects of work trip travel including travel times, mode choice, work schedules, absences from work, and route choice. Nearly 2,000 surveys from four different downtown area employers were analyzed. Results showed that many different changes in work trip travel behavior occurred. These changes contributed to the reduced congestion experienced during the Olympics. 

The most frequent changes include shifts in the work schedule and higher than usual absences from work. Modal shifts and change in route choice were much less common. Results also show that employers had a significant influence on the strategies chosen by employees. The paper concludes with a discussion of the significance of the research findings.

Most of the equilibrium traffic assignment models used nowadays, are based on aggregate link performance functions. These flow-delay functions represent a crude abstraction of real dependence of travel time on actual traffic volumes and physical conditions of the transportation network elements. These link performance functions reflect the travel impedance associated with the links and intersections. In many applications, especial those which are concerned with detailed microscopic traffic analysis, the performance of these simplified flow-delay relationship might be too crude and thus unsatisfactory. When such analysis is desired, detailed flow-delay models, or simulation models, have to be used. Furthermore in many investigations different levels of detail are necessary for various components of the network. The flow-delay characteristics of some network elements can be represented by crude aggregate relations while other elements need to be represented in great detail and accuracy. When some, or all, of the network elements are not represented by mathematically defined flow-delay function it becomes very difficult to solve for user equilibrium in a transportation network. Similar difficulties might arise in the investigation of system optimum of transportation, communication or other networks. 

In the framework of this work, a traffic assignment model is developed that can be based on functions, whose exact mathematical form is not known. The proposed solution method applies to steady state network flow problems. This solution will be valid as long as the flow-delay curve is non deceasing when traffic flow increases. The flow-delay function can be numeric pointwise function or a set of simulation-generated values. The empirical analysis and derivation of the proposed solution methods follows the user equilibrium, traffic assignment model, developed by Leblanc [7].

This paper addresses deficiencies found in the current practice of highway geometric design and presents an alternative approach which achieves more meaningful and cost effective design. Current design practice suffers from vague definition of the design speed concept, is very inflexible, is insensitive to traffic volume and composition, does not explicitly consider cost factors, and is very costly. These deficiencies are primarily attributed to the deterministic approach utilized by current design practice. While all factors involved in the geometric design process (i.e., speed, friction, reaction time, etc.) are stochastic in nature and are fully distributed among the road users, the current approach relies on a single arbitrarily chosen value to represent each factor. 

This paper presents an alternative approach to geometric design of highways. This approach is fully sensitive to the real conditions of the design problem at hand (i.e., the traffic volume and composition), because it incorporates the stochastic nature of the various factors involved into the design process. The proposed approach also achieves an optimal, or a cost-effective, design which takes into account all the cost elements associated with the highway. An empirical example of horizontal curve design is presented to demonstrate the advantages of the proposed approach.

This paper takes a fresh look at the arguments against path-enumeration algorithms for the traffic assignment problem and provides the results of a gradient projection method. The motivation behind the research is the orders of magnitude improvement in the availability of computer storage over the last decade. Faster assignment algorithms are necessary for real-time traffic assignment under several of the proposed Advanced Traffic Management System (ATMS) strategies, and path-based solutions are preferred. Our results show that gradient projection converges in 1/10 iterations than the conventional Frank-Wolfe algorithm. The computation time improvement is of the same order for small networks, but reduces as the network size increases. We discuss the computer implementation issues carefully, and provide schemes to achieve a 10-fold speed-up for larger networks also. We have used the algorithm for networks of up to 2000 nodes on a typical computer work station, and we discuss certain data structures to save storage and solve the assignment problem for even a 5000 node network.