Traffic Diversion Methodology
Once it was determined how much traffic would divert and the primary routes that would be utilized, a comprehensive evaluation of the impacts to the diversion routes was undertaken. The graphic below highlights the key methodology for the evaluation of the diversion route.
Route Identification
Prioritize routes that add more than 100 vehicles per day
Traffic Projections
No toll vs tolling scenario comparisons
Route Conditions
Intersections, traffic control, signage, & pavement conditions
Crash Data Summary
Identify crash patterns & crash rates
Capacity Analysis
Depict operational issues & capacity limitations
Roadway Review
Evaluation of lane widths and pavement structure
Alternative Transportation Modes
Transit, bus, bike lanes, etc.
Potential Mitigation Options
Evaluation of options to offset impacts to community
A workshop was conducted with key stakeholders in July 2021 to get feedback on the diversion route analysis and collect additional information on routes drivers might take, and potential impacts from diverting traffic. This feedback was incorporated into the traffic diversion analysis and evaluated to identify improvements PennDOT could consider to mitigate effects on the community caused by toll diversion.
Traffic Evaluation and Diversion Route Improvement
An extensive traffic study was conducted of the likely diversion routes, which are varied given the grid-like roadway system in the area, including field observations and stakeholder coordination, traffic counts, capacity analysis, and crash analysis.
Intersection turning movement counts were conducted at 30 intersections in the vicinity of the I-83 bridge that are likely to be impacted by traffic diverting to avoid tolling, as shown on the Diversion Route Map, during the AM peak and PM peak periods. These count locations were selected by PennDOT to capture the routes expected to be most impacted by traffic diverting from the I-83 bridge due to tolling. These counts included separate tabulations of pedestrians, motorcycles, cars, trucks, medium trucks, and heavy trucks. Video was taken during the counts to document traffic operations.
Capacity analysis was conducted of these 30 intersections using a traffic operations model. Increased traffic along the area roadways as a result of traffic diverting from the I-83 bridge to other alternatives, including primarily the Market Street Bridge and the Harvey Taylor Bridge was estimated using the Tri-County Regional Planning Commission Harrisburg area model.
The capacity analysis indicated that 23 of the study intersections would maintain a similar level of congestion or that congestion increases could be managed with signal timing optimization. At the seven intersections listed below, overall delay is expected to increase in the future with the projected diversions:
- Erford Road and Camp Hill Bypass [West Shore Intersection #01]- Although the delay will increase, this intersection will continue to operate acceptably.
- S. 3rd Street and Herman Avenue [West Shore Intersection #31]- Intersection delay will increase, however, based on the roadway grid network, drivers on both sides of S. 3rd Street have access to the existing traffic signal at the intersection of S. 3rd Street and Hummel Avenue, located two blocks north of Herman Avenue. This signalized intersection is an alternative for drivers turning onto S. 3rd Street if the delay at the stop-controlled Herman Avenue becomes excessive.
- Camp Hill Bypass and Harvey Taylor Bridge Bypass and 21st Street [West Shore, Combined Intersections #02 and #03] - Geometric constraints abutting this intersection make additional improvements impractical.
- Market Street and Front Street [East Shore Intersection #10] - Physical improvements are impractical given the geometric constraints at this intersection, including the Market Street Bridge and its abutments. It should be noted that while intersection delay will increase at this location, it is expected to be minor.
- Forster Street and Front Street [East Shore Intersection #17] - Physical improvements are impractical given the geometric constraints at this intersection, including the Harvey Taylor Bridge and its abutments.
- 32nd Street and Market Street [West Shore Intersection #28] - Physical improvements to this intersection are impractical given the location of development abutting the approaches to this intersection.
- 32nd Street and Trindle Road/Chestnut Street [West Shore Intersection #29] - Physical improvements to this intersection are impractical given the location of development abutting the approaches to this intersection.
The crash analysis looked at five years' data of reported crashes throughout the study area. Multiple crash clusters have been noted throughout the study area, which is not unexpected given the volumes of traffic and number of conflicting movement throughout the area. The largest clusters are noted on the east side of the Harvey Taylor Bridge at Front Street and along N. Cameron Street, between Elmerton Avenue and Maclay Street.
Programmed Improvements
Several improvements are programmed to be completed within the next few years within the area of the I-83 bridge and the areas expected be impacted by the projected diversion traffic. Notable improvements include the following projects:
- Cameron Street Improvements - Intersection improvements at Cameron Street/Maclay Street/Arsenal Boulevard and signal improvements along Cameron Street corridor
- Capital Gateway Improvements - Bicycle/pedestrian improvements along Forster Street from Susquehanna River to 2nd Street
- Derry Street Safety Improvements - Safety improvements along Derry Street from 13th to 40th Streets
- I-83 East Shore Sections 2 and 3 - Widening of I-83 to provide additional travel lanes in each direction and improvements to the interchanges from South Bridge to Eisenhower Boulevard (all interchanges). Learn more on the I-83 Beltway Projects website.
- Lemoyne Bottleneck Improvements - Bicycle, pedestrian, and safety improvements on Market Street, from Bosler Avenue to Front Street.
- Maclay Street Bridge - Bridge replacement over the Norfolk Southern railroad
- Market Street Bridge - Bridge rehabilitation over Susquehanna River
Key Issues
Through input provided at the diversion workshop and through the traffic analysis and crash evaluation, several issues have been identified throughout the project study area. The following is a listing of the major identified issues along with a brief discussion on how those issues are expected to be addressed.
Market Street operation in Lemoyne [West Shore]
- Issue - Traffic signal operation creating bottlenecks
- Resolution - Construction of the Lemoyne Bottleneck Improvements project should improve the bicycle and pedestrian operations in this area of Market Street.
Forster Street, at Front Street and 2nd Street [East Shore]
- Issue - Overall traffic operation issues
- Issue - Bicycle and pedestrian safety
- Resolution - Traffic operations and overall safety should be improved with the Capital Gateway Improvements Project and traffic signal optimization proposed in conjunction with the I-83 bridge tolling.
Cameron Street and Maclay Street/Arsenal Boulevard [East Shore]
- Issue - Overall traffic operation issues
- Resolution - Construction of the Cameron Street Improvements project should improve the traffic operations along Cameron Street.
Select West Shore signalized intersections [West Shore]
- Issue - Overall traffic operations
- Issue - Inadequate traffic signal coordination
- Resolution - Signal timing optimizations proposed in conjunction with the tolling, which include coordination improvements, should improve overall traffic operations in this area.
PA 581 merge with WB I-83 [West Shore]
- Issue - Short merge creates traffic backups
- Resolution - Diversion of traffic away from I-83 due to the tolling will reduce I-83 traffic volumes, which will improve the operation of this merge.
32nd Street at Market Street and Chestnut St/Trindle Road [West Shore]
- Issue - Overall intersection operation
- Resolution - Traffic signal timing improvements should help alleviate this concern. Development constraints adjacent to this intersection limit the ability for further improvement.
Front Street and Market Street [East Shore]
- Issue - Overall intersection operation
- Resolution - Traffic signal timing improvements should help alleviate this concern. Geometric constraints adjacent to this intersection limit the ability for further improvement.
S. 3rd Street at Herman Avenue [West Shore]
- Issue - Bicycle/pedestrian safety to cross S. 3rd Street due vicinity of pool and park
- Resolution - Installation of Rectangular Rapid Flashing Beacon (RRFB) should help improve the visibility of the crosswalk and people crossing S. 3rd Street at this location within the crosswalk.
Camp Hill Bypass/Harvey Taylor Bridge Bypass and 21st Street [West Shore]
- Issue - Overall intersection operation
- Resolution - Traffic signal optimization and potential inclusion of this intersection within the Camp Hill Bypass adaptive signal system should help improve the operation of this intersection. Development and geometric constraints limit the ability of additional improvements at this location.
N. 7th Street and Walnut Street [West Shore]
- Issue - Crossing guard safety given crash history
- Resolution - Coordination with the municipality to improve crosswalk striping and signage to be in conformance with current standards should provide improvement at this location.
Proposed Diversion Route Improvements
In summary, the following is a listing of the proposed diversion route improvement measures proposed in conjunction with the I-83 bridge tolling:
- Traffic Signal Optimization:
- Market Street and 21st Street [West Shore Intersection #4]
- Market Street and 12th Street [West Shore Intersection #5]
- Market Street and 3rd Street [West Shore Intersection #6]
- 3rd St and Lowther Street [West Shore Intersection #7]
- Market Street and Front Street [West Shore Intersection #8]
- Front Street and Market Street [East Shore Intersection #10]
- 2nd Street and Pine Street [East Shore Intersection #13]
- Forster Street and 2nd Street [East Shore Intersection #16]
- Front Street and Forster Street [East Shore Intersection #17]
- Cameron Street and Market Street [East Shore Intersection #21]
- Cameron Street and Herr Street [East Shore Intersection #22]
- Forster Street and 7th Street [East Shore Intersection #27]
- 32nd Street and Market Street [West Shore Intersection #28]
- 32nd Street and Chestnut Street/Trindle Road [West Shore Intersection #29]
- Install flashing beacon at S. 3rd Street and Herman Avenue for pedestrian/bicycle crossings of S. 3rd Street [West Shore Intersection #31]
- Review clearance interval timing at Forster Street and Front Street [East Shore Intersection #17]
- Coordinate with municipality to improve crosswalk paint and signage near N. 7th Street and Walnut Street [West Shore]
- Consider incorporation of the intersection of Camp Hill Bypass/Harvey Taylor Bridge Bypass/21st Street into Camp Hill Bypass Adaptive Signal System [West Shore Intersections #21 and #22]
- Conduct before/after study of intersection operations - Because modeling forecasts can sometimes differ from actual impacts, before and after studies will be conducted on the diversion routes. These studies will confirm the models' results or identify areas where additional evaluations should be conducted to identify improvements for consideration and potential implementation.