by Anitha Balasubramanian

The LTV Steel South Side Works is a 130 acre undeveloped land, along East Carson Street and the Monongahela River, in the City of Pittsburgh.

Originally the site for J&L Steel, it now lies as a brownfields, with ample scope for redevelopment. The site had been owned by the LTV (Ling-Temco-Vought) Corporation since 1974 and used for steel production. The site was purchased by the Urban Redevelopment Authority of Pittsburgh (URA) in 1993 for redevelopment.

One of the possible problems that could arise as a result of the redevelopment is the additional traffic generated. At present, East Carson Street is the only road which provides access to the LTV site. East Carson is already a heavily travelled, congested street. The amount of additional traffic that can be permitted on the East Carson Street depends upon the improvements and additions that can be made to the road system surrounding the site.

In order to examine the result of the increase in traffic, the traffic simulator program MITSIM, has been used in the case study. This facilitates study and evaluation of the traffic impacts, and the development of traffic control strategies at a local level around the brownfields. The area modeled consists of the East Carson Street between 22nd Street and Becks Run Road. Traffic counts for the area considered were obtained from the Department of City Planning for the city of Pittsburgh. Blueprints of the streets within this area, with information regarding street layout, and also timing table data for signalized intersections, were obtained from the City of Pittsburgh’s Department of Engineering and Construction.

For an efficient modeling of the network, input files for the network data, traffic signal controllers, and time dependent origin destination trip data were created. Number of test runs were conducted to collect data with variations in the travel demand. The simulation was run for an hour from 9:55 to 10:55. The travel demand was varied in uniform increments. At least 3 sets of data were obtained for each increment of travel demand and the average was taken for data analysis. The simulator settings were modified so that the average travel time over any given link is reported in intervals of 10 minutes over the entire simulation process. The objective of data collection using traffic simulator is to determine the adequacy of the existing infrastructure with increase in travel demand.

Considerable amount of time was spent to achieve a realistic model of the road network under consideration. The analysis of link specific travel time, combined with visual inspection of the simulation operations, revealed that there was an error in the travel time calculation methodology used by the simulator. The simulator reported free flow travel time, when no vehicle is reported to have crossed the link, in the given time interval. This does not take into consideration, the lack of movement of vehicles owing to queuing. The modified calculation methodology depends on the average travel time of vehicles entering the link in the previous and the next time intervals.

Since the simulator was originally developed for freeway traffic, relaxations had to be imposed on the lane connectivity data, so as to get a realistic model of the network intersections.

The traffic impact assessment studies revealed that changes made to the infrastructure (such as green time modification of signal settings), at selected areas on the network, leads to improvement of performance in the immediate vicinity, but is likeely to produce deterioration elsewhere on the network, and posssibly in the road system beyond the scope of the modeled area. It is therefore necessary to study the impact on the system as a whole, in addition to monitoring its individual components. Traffic simulator models such as MITSIM facilitate this approach.

A detailed report of the traffic impact assessment of the LTV case study, is provided in the report, "Transportation Infrastructure Evaluation and Traffic Impact Assessment for Brownfields", M.S. thesis, Anitha Balsubramanian, Carnegie Mellon University, Pittsburgh, Aug 1998.

The report also details the development of an emission model application to determine the pollutant emission that may be produced due to urban traffic.