State officials have said they will make their decision about what will replace the Casey Overpass by the end of this month.

Two options remain: Either a new, lower bridge would be built or a network of surface roads would replace the current configuration.

This week the State Department of Transportation issued a list of "Frequently Asked Questions," that give the department's responses in detail.

The document tackles a wide range of questions about traffic, design and process. For instance, to the often-expressed question about how can traffic possibly not be made worse by putting bridge traffic onto the surface streets, the department says:

Today’s congestion is the result of a poorly-designed surface street system. That system will be replaced with a new, more logical, street system with either alternative.

The department also responds to critics of their process, who allege that the design team has been biased against a bridge solution from the beginning.

A bridge alternative was known to be viable from the start. Whether a viable design for an at-grade alternative was even possible was an unknown at the beginning of the process. Concepts needed to be worked out and analyzed to answer that question. It was not until spring 2011 that a workable at-grade solution was developed.

The text of the nine-page document is below. To see it in its original form, view the attached PDF.

For much more on this key issue facing Forest Hills, see the JP Patch topic page on the Casey Overpass and the Department of Transportation Web site devoted to it.

Frequently Asked Questions

Casey Overpass Planning and Concept Design Study (as of 02/15/12)

Traffic Questions

Question - Does the bridge alternative provide for faster trips?
Response – A bridge would be speedier for regional trips using the viaduct. The advantage would be between 30 and 90 seconds at rush hour. That advantage may be negated by delays at Murray Circle.
Local trips made on surface streets would be similar for both the at-grade and bridge alternatives. Both options provide significant improvement over the existing conditions. North/south traffic would experience the exact same number of signals it does today and be able to make all of the same turning movements.

Question - Will traffic backing up from Murray Circle extend back to South Street or onto the overpass and complicate operations in the future?
Response - The queue from Murray Circle has been observed extending to approximately the end of the ramps from South Street where they connect to the Arborway. It has not been observed extending past South Street. There is queuing that occurs on the Overpass near Shea Circle, but that queue is a result of delays within the temporary lane merge on the overpass and from the rough surface on the overpass. The potholes on the bridge are causing vehicles to slow as they travel over these locations and this slowing produces denser traffic. At the end of the actual overpass, vehicles break free for a brief period before hitting the back of the queue from Murray.

Question – How do the 2035 traffic projections account for future growth?
Response - 2035 traffic volume growth assumptions are based on traffic counts from June of 2010 (made when school was still in session). These counts formed the base line for 2035 traffic volumes, which were then calibrated with the assistance of BTD, BRA and CTPS to account for anticipated development. The Central Transportation Planning Staff (CTPS) holds the regional traffic model for all of eastern Massachusetts and this model projects future traffic volumes, taking into account economic fluctuations and mode shifts. The changes in traffic volumes caused by economic fluctuations is one of the reasons traffic has been modeled for 24 years in the future and not simply for 2016 when the selected replacement for the Casey Overpass will be in place. In addition to the regional traffic volume increases projected by CTPS, traffic from identified local development projects were added to form the 2035 traffic volumes.

Question - How good are the CTPS projections?
Response – They are reliable and are the standard that is applied to major transportation projects in this region. For example, the CTPS traffic projections for the Central Artery project developed in the 1980s used a build year of 2010. These projections were compared to actual 2010 traffic counts and showed that the CTPS model had overestimated the number of vehicular trips by approximately 13%.

Question – Do the U-turns in the at-grade alternative cause significant delays for drivers?

Response – The U-turns—also referred to as bow ties—require some drivers to travel longer distances but do not add to travel time. Overall, the trips made on surface roads are comparable between the two alternatives. Depending on the point of origin and the desired destination, some trips are quicker with the bridge alternatives and others are quicker with the at-grade alternative. A detailed comparison can be found in the Alternatives Analysis Technical Memorandum on the project web site at http://app1.massdot.state.ma.us/CaseyOverpass/downloads/Casey_Traffic2_092211.pdf on pages 11, 12 and 13.

Question – Today’s traffic is so bad, how can putting the viaduct traffic on the surface not make things worse?

Response – Today’s congestion is the result of a poorly-designed surface street system. That system will be replaced with a new, more logical, street system with either alternative. For both alternatives local traffic conditions will improve significantly. See the links in the response above for details.

Question – Will putting all the viaduct traffic on local streets create more congestion and cause drivers to divert onto local neighborhood streets?
Response – No. Each alternative is capable of accommodating projected traffic demands. Alternate routes remain less desirable for motorists than to remain on the proposed roadway networks. The lack of diversions was confirmed by the local traffic study and through CTPS’ regional model.
To identify the potential for vehicle diversions and the sensitivity of the regional model to assess the diversions, a test model run was performed with the Casey Overpass removed, but no changes made to the surface streets. Under that test case, a significant portion of the traffic using the Casey Overpass diverted away from the study area. This test run demonstrated that if delays were increased appreciably, vehicles would divert to other roadways.

Question – Are the traffic volumes counted for this study significantly lower than those counted in previous studies?
Response - The traffic volumes counted for this project are comparable to the volumes counted during the 2007 Structural Condition Study with overall peak hour volumes within 2-3 percent.
The Arborway Master Plan was conducted in 2002 and included additional traffic counts in the vicinity of the Casey Overpass. This report cited a daily volume of 34,000 vehicles per day (vpd) on the overpass, compared to 24,000 vpd counted as part of the current study. The counts conducted for the 2002 report did not include an actual count on the overpass and the 34,000 estimated was extrapolated from other counts and it appears to be overstated. A comparison of the peak hour traffic volumes to and from the overpass at Shea Circle show volumes are within 10-15% of those counted for the current study. While it is possible that the volumes on the overpass were higher in 2002 than they are today, it appears that the 34,000 vpd estimate is severely overstated. (Even a 15% increase over current volumes would have only been 27,600 vpd.) It’s worth noting that in 2002 the Central Artery Project was in the midst of construction and traffic patterns have shifted with the completion of the Central Artery project and these shifts may have contributed to any decrease in traffic volumes that have occurred on the overpass from 2002.

Question - Why did the previous studies conclude that an at-grade solution was impossible, but the current study has presented an at-grade solution as feasible?
Response - The previous study, conducted in 2008, had a number of differences from the current study. It assumed that the Casey Overpass would remain in its current configuration and that assumption limited the options available. The 2008 study considered 3 at-grade configurations: roundabout intersections; traditional intersections; and a signalized rotary with service roads. Each of these alternatives had fatal flaws. The 2008 study did not examine the opportunity to relocate MBTA infrastructure presenting better options for roadway designs, pedestrian and bicycle circulation and open space connections.
The current study took a much broader approach to potential solutions and developed the median U-turn (“bow-tie”) concept that accommodates vehicular traffic significantly better than previous alternatives.

Question - Are the surface roadway traffic volumes with the bridge alternative significantly lower than with the at-grade alternative?
Response - The east-west through volumes on the surface street are lower with the bridge alternative. All north-south volumes and all turning volumes are the same between the two alternatives. The east-west through movement constitutes about ½ of the total volume traveling through the intersections for the at-grade alternative, so the total volumes within the intersections for the bridge alternative is approximately 50% of the at-grade alternative.

Question - Will the pedestrians be able to cross the roadways within a single walk cycle or will multiple cycles be required?
Response - The pedestrian timing is intended to be sufficient to allow pedestrians to fully cross the roadway within a single cycle under either alternative. A walking speed of 3.5 feet per second was used. The 3.5 feet per second walking speed accounts for slower walkers such as senior citizens and parents walking with young children.

Question - Currently signals in the area are synchronized for north/south (N-S) movement & under either alternative- will signals be synchronized for east/west (E-W) movement?
Response - The existing roadway geometry and proximity of the signalized locations makes effective coordination of the signals very difficult. Either alternative will improve upon the roadway geometry and allow better overall signal coordination, which will be balanced to provide for all vehicles to traverse this area.

Question - How many signals would be encountered when traveling through this area?
Response - The number of signals in the N-S direction does not vary between the alternatives and with the exception of geometric improvements to the intersections; the number of N-S signals does not change from existing conditions. In the E-W direction, the bridge alternative maintains the existing number of signalized intersections (exclusive of what is determined for Shea Circle). The at-grade alternative adds the two signals for the E-W U-turn movements. However, these signals would only stop through traffic in one direction, resulting in through traffic effectively experiencing only one additional signal with the at-grade alternative.

Question – East/West Backups on the Arborway- AM Backups on the Arborway from the Murray Rotary don't appear in traffic models or animations for either bridge/no bridge solution. PM backups from the Shea Rotary also occur. These backups can extend back over the whole Casey Overpass. They are not reflected in the traffic models/simulations we've seen.
Response – Field measurements of delay at Murray Circle and Shea Circle were conducted by the project team in September of 2011. Delay at Murray Circle was again measured on October 24, 2011. The Murray Circle delays were included in the latest iterations of the traffic modeling and animations that were presented at the November Public Meeting.
The queue from Murray Circle has been observed extending to approximately the end of the ramps from South Street where they connect to the Arborway. It has not been observed extending past South Street. There is queuing that occurs on the Overpass near Shea Circle, but that queue is a result of delays within the temporary lane merge on the overpass and from the rough surface that was on the overpass.
The treatment for Shea Circle is interchangeable with both the at-grade and bridge alternatives. Therefore, the selection of improvements for Shea Circle was deferred until after a selection has been made between the at-grand and bridge alternatives. As the project advances, the alternatives for Shea Circle will be further refined and modeled for presentation to the public.

Question – Are there impacts from traffic backups at the Left Turn Bowties; at North/South arterials, on traffic seeking alternate routes?
Response – The left-turn bow tie intersections are projected to operate at good levels of service with reasonable queues that do not extend to adjacent intersections. Overall, traffic operations improve for the build conditions over the no-build condition, including the north-south operations, and all queues are managed to avoid spillback to adjacent intersections. The at-grade alternative offers additional capacity to the northbound and southbound approaches at the New Washington intersections with South Street and Hyde Park Avenue in comparison to the Bridge concept.
As for traffic seeking alternate routes, since the overall travel times in the study area are not expected to change significantly, the project is not expected to increase the desire for cut through activity. The project team conducted travel time runs of alternate routes through the adjacent neighborhoods and found that in all cases the “cut thru route” took longer to travel than remaining on the Arborway under either build alternative.
CTPS’s regional traffic model also analyzed regional travel times for the study area and the surrounding roadways and found that the proposed alternatives do not alter regional travel times and would not cause diversion to alternate, “cut-thru” routes.

Question – Bus movements and Preferential Signaling vs. Synchronized Signaling - Bridge or No Bridge, regular and frequent rush hour movements of 3 bus routes from Mattapan and Dorchester in addition to the #39 bus haven't been addressed in traffic models or simulations. Bus movements at the upper Forest Hills Station deck haven't been addressed in traffic models or simulations? - Will preferential traffic signaling for buses at New Washington St./Hyde Park Ave interfere with synchronized movement of traffic throughout the Forest Hills area?
Response – The latest iteration of the modeling and associated animations that were prepared and presented during the planning phase for both the at-grade and bridge alternatives included the bus pre-emption. The traffic signal operations and coordination account for the bus pre-emption phases, which are of short duration, are not required in every cycle, and are therefore not expected to significantly affect the synchronization of the traffic signals.
Although the traffic simulations focused on the east-west corridor, traffic operations of the entire study area were analyzed using SYNCHRO capacity analysis. The analysis included the intersections of Washington Street and the MBTA station driveways.

Question – Will bus movements at the upper FHS deck interfere with traffic movements through the Forest Hills area?
Response – For the Bridge Alternative, the locations of the FHS driveways on Washington Street remain unchanged, with the northern access intersecting Washington Street opposite South Street.
For the At-Grade Alternative, the FHS driveways on Washington Street have been shifted south and the bus berths have been re-designed to include additional capacity. The bus egress is no longer opposite South Street, reducing the conflicts at the Washington Street/South Street intersection, which improves operations. Also, taxi stands and pick up drop off areas have been designated on Washington Street. These improvements are expected to improve the overall operations along Washington Street under the at-grade alternative.

Question – Traffic Mitigation - Neighborhoods and commuters are concerned that traffic mitigation measures be designed and completed before the start of the bridge demolition.
Response – Construction sequencing and traffic management during construction has not yet been designed. These tasks will be started in the 25% design phase and the goal for either alternative will be to minimize construction impacts and duration.

Question – Traffic calming measures to improve safety in the study area are wanted. Are these adequate to mitigate any traffic impacts?
Response – Traffic calming measures and many other design details will be investigated and incorporated, as appropriate, during the detailed design phase, beginning with the 25% design.

Design Questions

Question - Are right-turn “slip lanes” necessary to make the alternatives work?
Response - The right-turn slip lanes are currently shown on each alternative and these right turn movements would be fully signalized to provide protected pedestrian crossings. The demand for these slip lanes is dependent on right turning volumes and pedestrian activity. Neither of these factors change whether the at-grade or bridge alternative is selected as all turns will occur at the at-grade intersection in either alternative. As such, the treatment of the right turn lanes is to be determined in the 25% design stage.

Question – What is the cost of each alternative?

Response – The consultant team’s estimated order-of-magnitude costs based on conceptual designs for the at-grade and bridge alternatives are: are $74 million for the bridge and $53 million for the at-grade. The values for the estimates are based on current 2011 dollars.

Question – The WAG asked the project team for specific costs on various elements of the project? Sometimes, the committee has needed to wait for a response, why is this?

Response – As this project has not yet even reached the 25% design stage, it is far easier to arrive at general costs for each alternative than to come up with specific costs for the different components that make up the project. The project team has been careful only to provide numbers once they have achieved some level of certainty about them and only then while making it clear that these figures may change as the project achieves higher levels of detail. The project team could not supply order of magnitude cost estimates until the two alternatives were defined.

Question - How do the alternatives compare when life cycle costs are factored in?
Response - The life cycle costs for a bridge are appreciably higher than those for an at-grade roadway. Bridge life cycles are typically considered to be 75 years. For this project, the future maintenance and repair costs for the bridge alternative would be approximately $30-$35 million more than the maintenance and repair costs for the at-grade alternative over the life cycle of the project. (Additionally, the bridge would then presumably be replaced again at the end of the 75 year life cycle.)

Question – Will the at-grade alternative be worse for pedestrians and cyclists?

Response – The volume of vehicular traffic anticipated is no greater than on many other city streets that are enjoyed by all users and support active uses. The roadway designs are based on 25-30 mph speeds. The WAG required that pedestrians and bicycles be addressed thoroughly for each alternative and that the surface street designs in both alternatives accommodate pedestrians and cyclists. Most pedestrian and bicycle advocates favor the at-grade solution.

Question – Will the two designs for Shea Circle: Shea Square and the Eggabout work for each alternative?
Response – Yes. They are inter-changeable designs.

Question - Is Shea Circle protected as a historic resource?
Response – Shea Circle is listed as a contributing factor to the Emerald Necklace which is listed on the National Register of Historic Places. Preliminary outreach to the Massachusetts Historic Commission suggests that modifying the circle to the “Egg-a-bout” concept could be accomplished without needing to go through any review process. Making Shea Circle into Shea Square, a four-way signalized intersection, would in all likelihood be seen as a negative impact from a historical point of view and require a review process. However, it is anticipated that the impact would not be so great as to stop the change from circle to square, particularly if there was strong community support.

Question - Is the median U-turn designed to accommodate trucks?
Response - Yes. While the design is preliminary, truck turning movements have been assessed to confirm they can U-turn within the area provided.

Process questions

Question – Did MassDOT start this process with a preference for a surface option?

Response – No. A bridge alternative was known to be viable from the start. Whether a viable design for an at-grade alternative was even possible was an unknown at the beginning of the process. Concepts needed to be worked out and analyzed to answer that question. It was not until spring 2011 that a workable at-grade solution was developed. In addition to the traffic issues, there were a number of other challenges for an at-grade concept which required cooperation with the MBTA to resolve such as the relocation of the MBTA headhouse, emergency vent stacks for the Orange Line and commuter rail vent grates.

Question – Is the design team and MassDOT biased toward the at-grade solution?
Response – No. Throughout the 9-month study, the design team presented many concepts to explore the questions raised by the community for bridge and at-grade alternatives. Members of the design team include urban design, traffic and bridge engineer professionals. The activities of the design team have been in large part directed by the concerns and questions of WAG members and have to a great extent reflected their questions and concerns, particularly with regard to specific areas within the corridor that present problems today.

Question - Will there be an environmental assessment and should that be done before an alternative is selected?
Response - One of the next steps as the project advances to 25% design will be to prepare an Environmental Notification Form (ENF) for submission to the Massachusetts Environmental Policy Act (MEPA) Office. The exact scope of that document has not yet been determined, but it is anticipated that an air quality analysis will be included. The air quality analysis is a direct result of the traffic operations analysis. As part of CTPS modeling efforts, they produced the air quality results for the two alternatives and determined that the overall air quality effects were comparable. As the air quality analysis is directly dependent on the traffic analysis, it stands to reason that as the traffic operations are comparable, the air quality results will be similarly comparable.

General Questions

Question – Would BTD be responsible for the street network?

Response – MassDOT would be responsible for the design of the street network; DCR would be responsible for maintenance of any at-grade E-W roadways (New Washington Street). BTD would operate the traffic signals. BTD is responsible for the north/south roadways.

Question – How have transit issues been address for this project?
Response – The project team has worked extensively with the WAG on transit. One of the goals for the project as defined by the WAG was to maintain or, if possible, improve transit operations at Forest Hills Station. Special provisions have been included in the at-grade concept to allow buses coming from the east to make left turns to access the lower bus-way at Forest Hills Station. The at-grade concept also provides for additional transit improvements to Forest Hills Station’s upper bus-way and improved access to the Orange Line from South Street and the Southwest Corridor Pathway. Both options show the Route 39 bus operating on New Washington Street, close to its current location, and using a queue jump-light to turn around at the Hyde Park Avenue intersection.

Question – Can you provide additional time review of the Measures of Evaluation (MOE)?
Response – The MOE were developed and fully reviewed over the previous nine months. They were developed by WAG members and updates were provided at nearly every WAG meeting along with extensive documentation, which was made available to the public on the project web site. Suggested additions to the MOEs were considered and adopted if they had measurable data
and sources for the data. Each MOE was carefully examined to eliminate duplication and to be able to have meaningful results in evaluating each alternative and existing conditions. WAG members contributed significantly to the development and evolution of the MOEs as well as submitted new measures.