Improvement, Aquarium parking and traffic can be accommodated either In the Navy 

 Yard, under the Tobin Bridge or at Hayes Square. 



The other key Intersection Involved In the analysis Is the City Square 

 Intersection, which Is being reconstructed as part of the CANA project. in 

 evaluating City Square, a PM peak hour of 4:30 PM to 5:30 PM was used. Background 

 volumes were factored to account for the fact that overall PM peak hour traffic Is 

 approximately 9X lower In August than In an average month. August, however. Is the 

 peak month for Aquarium visitation. 



The City Square Intersection will connect Rutherford Avenue, the Charlestown 

 Bridge to Boston, the ramps to and from 1-93 and Chelsea Street. It Is anticipated 

 that most of the traffic travelling to and from the Navy Yard will pass through 

 this Intersection. Under other project designs the Intersection was projected to 

 operate at level of service 'F', according to an analysis conducted for the Boston 

 Transportation Department (BTD) . As a result, the BTD has proposed a redesign 

 which would operate at level of service 'D', although three Individual moves would 

 operate at 'E' or 'F'. This design, which Involves minor widenlngs, addition of 

 turning lanes and removal of some parking on Chelsea Street, has not yet been 

 accepted by the Massachusetts Department of Public Works. 



The amount of peak traffic added to City Square from the Aquarium would be 

 rough ly the same, regardless of parking facility iocat ion. At 2.1 million visitors 

 per year the overall level of service at City Square will remain at level of 

 service 'D' although three additional moves will decline from level of service 'D' 

 to level of service 'E'. This makes a total of five moves at level of service 'E'. 

 It Is important to note, however, that this analysis Is based on conservative 

 assumptions. Including one related to the analysis technique itself. The level of 

 service analysis assumes a "saturation flow rate" of 1800 vehicles per hour per 

 lane. This is a nationally recognized standard, but there Is evidence that the 

 actual rate in the Boston area is higher at some locations. This means that more 

 vehicles may actually get through an Intersection than is being assumed In the 

 analysis. If a higher saturation flow rate Is used, the delays shown for City 

 Square In Table 7 would be lower. 



Table 8 summarizes the level of service for a summer Saturday peak hour. 

 Aquarium traffic Is highest on Saturday, although background traffic is 

 considerably lower than during the weekday peak hour. A set of traffic counts was 

 taken on a Saturday in July of 1988 to provide a basis for estimation of Saturday 

 background traffic. This base was then factored up to account for the proposed 

 build-out of the Navy Yard and Tudor Wharf. The analysis shows that the location 

 of a garage In the Navy Yard or under the Tobin Bridge would result in unacceptable 

 congestion at Gate 4/Chelsea Street on Saturdays. If the Fifth Street approach and 

 the Intersection Itself are Improved, however, a sat Isfactory level of service will 

 be achieved. 



Vanasse Hangen Brustlln, Central Artery North Area Local intersection 

 Ana lysis, prepared for Boston Transportation Department, November, 1987. 



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