Topics of Interest
Traffic
An increase in housing concentrated around Lincoln Station will coincide with an increase in cars and related traffic.
Traffic implications of development allowed by Article 3 (aka Option C) merit full review so that everyone in Lincoln understands the real consequences of zoning for 650 - 800 units of new housing around Lincoln Station.
In discussing Article 3, The Planning Board has cited a traffic study that was commissioned in 2019 and conducted in December 2019 - January 2020. Since then, cut-through traffic from new developments in adjacent towns has increased and COVID-19 has brought many changes in how most people conduct their daily lives. These changes were beyond prediction, and it seems overconfident to rely on this 4-year-old-study as a basis upon which to make traffic assumptions related to Article 3's consequential rezoning in Lincoln.
But, because the Planning Board refers to this 2019-2020 traffic study when responding to concerns about traffic related to HCA rezoning, it merits your understanding so that you can consider the issue and make up your own mind about the quality of the study's design and its relevance to Option C rezoning.
Does this study address the ripple-effects of increased traffic on the Lincoln Road corridor in proportion to Article 3 rezoning?
Read the following detailed summary and analysis of the 2020 traffic study conducted 4 years ago to decide for yourself.
Under HCA guidelines every unit developed through this rezoning must have at least one parking space at minimum. This means that Article 3 also provides for an increase of 650 - 800 cars coming and going along the Lincoln Road corridor.
If Article 3 is passed, according to the Director of Planning, any future traffic studies could only result in mitigations, but not in decreased development allowed through the rezoning. One mitigation referenced for increased traffic pressure on the Lincoln Road corridor was the addition of a traffic rotary at the "Five Corners" flower pot in Lincoln's historic center. Is this what you had in mind when considering Option C in December? It's possible to comply with a more moderate HCA solution that helps Lincoln evolve while still preserving its essence.
What are your concerns about the ripple-effects of this kind of traffic on the Lincoln Road corridor and beyond?
Lincoln Road Mall Traffic: A Summary of the 2020 Analysis
By Robert Ahlert, 185 Lincoln Rd
In 2019, the Town of Lincoln Planning department determined that a traffic study of the Lincoln Station area would benefit the town. At this time, it is not known if an RFP was conducted to select the traffic engineer or if another approach was used to select the best fit traffic engineer for this particular study. By December 2019, we know that the study was initiated by Ron Muller Associates. No Build, 60% build, 100% build, with the 100% build at that time implying 250 units, which is roughly half as much is as (the +450 units) modeled in our HCA proposal.
What follows is a summary of this study focused on 5 topics:
Study Approach
Objective
Modeling
Recommendations from RMA (Ron Muller Associates)
Special Note: Multi-Model Level of Service (MMLOS) - A better way to measure
The study was conducted by Ron Muller and Associates of Hopkinton MA.
Study Approach
The study requested that the traffic engineer study 6 intersections on Lincoln Rd, going east to west, from 117 (West) to Wells Rd (East). In this study, North is considered the direction from Lincoln Rd towards 126, South is considered along Codman Rd to 117, West is considered the direction towards 117 along Lincoln Rd and East is considered in the direction of the School/Rt 2. See diagram to the Right -->
The following intersections were studied along Lincoln Rd (from West to East)
Codman Rd
Lewis St
Post Office Driveway
Ridge Rd
Mall Entrance
Wells Rd
As a baseline to understand the current Traffic Volumes in this area, two techniques were utilized:
TMC - manual turning volume and classification counts. Essentially an individual stands at an intersection at a particular time of day and manually counts car movements. Collected in January 2020
ATR - automatic traffic recorders. The Lincoln Police department places automated car tracking devices along roadways to collect volumes. Collected in December 2019
These volumes and movements were collected in December and January, traditionally low months for traffic volumes. Smartly, these volumes were adjusted up 12% to account for the fact these months are typically slow months.
Using the ATR data, A K-factor is calculated at intersections to provide a ratio of peak-hour (AM, PM) counts to total counts. This will be used somewhere later in the modeling.
Using the TMC data, a basic visualization can be drawn to understand volumes and movements. As an example, over 1000 cars currently use the intersection Lincoln Rd/Codman Rd during Peak PM hour going left, right or straight from all directions
Also observed were the train crossings and their impact to traffic queues, for example during Peak PM hour. During the 4:00 to 6:00 PM period, there are five train crossings, two inbound and three outbound, with two of those train crossings occurring during the weekday PM peak hour (4:00 PM – 5:00 PM).
The study notes that there are no bicycle lanes on Lincoln Rd and that there are five unsignalized pedestrian crossings across Lincoln Road within the downtown area with locations at Lewis Street, the Post Office (just east of the train crossing), Ridge Road, 152 Lincoln Road and St. Joseph Catholic Church.
The study makes the following assumptions about future conditions through 2030:
Assumption
Annual Average Traffic Rate growth = 1% annually. This assumption is reasonable given the net increase in families with children of driving age.
Concern
Assumption
Impacts from other planned developments in Lincoln or Nearby. This study assumes No impacts from Cold Brook Crossing (+274 units on 117 in Sudbury)
Concern
Assumption
Transit Oriented Development (TOD) Currently 70% of Lincoln residents Drive Alone for their commute vs only 8% take the Commuter Rail. This assumption is more realistic than the 20% cited later in study.
Concern
Study Objective
The objective of the study was to predict impact on traffic under various future conditions.
There are a number of KPIs/metrics used to analyze this impact:
Number of Vehicle Trips - predicted net new number of trips based on additional units
Volume to Capacity Ratio (V/C) - a value over 1.0 means the intersection is "saturated"
Average Delay (in seconds per vehicle)
Level-of-service (LOS) - explained in detail below
Queue (in ft) assuming 25 ft per vehicle
These KPIs were evaluated under 3 theoretical future conditions
No Build - accounting for general traffic increase of 1%
60% Lot Coverage - at the time of this study in 2020, this meant adding 240 net new Residential units on 4 parcels near Lincoln Station and no net new Commercial
100% Lot Coverage - at the time of this study in 2020, this meant adding 271 net new Residential units on 4 parcels near Lincoln Station with 14.5K sq ft net new Commercial
At the time of the study, below are the 4 parcels included. These have changed since with the Option C proposal from Fall 2023.
Level of Service
The best summary KPI of an intersection (from a vehicular perspective) is its LOS (Level of Service) which takes into account multiple variables:
The failing grade for vehicles is an “F” which is forced or breakdown flow.
Every vehicle moves in lockstep with the vehicle in front of it, with frequent slowing required.
Travel time cannot be predicted, with generally more demand than capacity.
A road in a constant traffic jam is at this LOS, because LOS is an average or typical service rather than a constant state.
For example, a highway might be at LOS D for the AM peak hour, but have traffic consistent with LOS C some days, LOS E or F others, and come to a halt once every few weeks
The Model
The model for calculating new trips uses 2 main assumptions:
Land Use (LUC) - Transportation Engineers (ITE) Trip Generation Manual were researched.
ITE land use codes:
LUC 220 provides trip generation characteristics for apartment units
LUC 820 provides trip generation characteristics for commercial retail developments
Internal Capture - Internal capture trips are defined as shared trips between various uses in close proximity that do not necessitate a separate trip to each use. Therefore, the total trip generation to the site reduced over that which would otherwise be calculated for each individual use. For example, some motorists ultimately destined for the grocery store in Lincoln Mall may also make stops at the Post Office or various commercial uses during the same visit
The results showed the following net new trips for each of the parcels within the study area:
The highest number of new trips was in the 100% scenario (274 units residential) with 107 new trips at a peak PM hour with 69 entering the 4 parcels and 38 leaving the new parcels.
Based on another external study and given the proximity to commuter rail, the study suggests 20% of these trips would be eliminated further reducing these trips. This study, completed by Mineta National Research Consortium and Rutgers University in 2014 found that “nearly 20-percent of those who lived within a half-mile of transit used transit to travel to work, compared to less than nine percent of those living more than a half-mile from a station”
This number of trips represents a 13% (107/808) PM Peak hour increase in traffic after build-out.
The prediction for trip distribution suggests 70% of the traffic will come to/from the Rt 2 area and 30% will come from the 117 area.
The increases in traffic predicted are in the range 10 to 76 vehicles on Lincoln Rd in the 100% build-out scenario.
Assigning Grades to Intersections
Next the LOS (Level of Service) was calculated with the net new trips on top of the existing traffic volumes to assign a grade to each intersection. Utilizing this, grades are assigned to each intersection.
In summary, here are the values for the key KPIs for one of the intersections to see how this works. Please note the descriptions for each directional movement below
Eastbound (EB Left) - traffic moving from 117 towards School/Rt2 taking a left at the intersection noted
Westbound (WB Left) - traffic moving from School/Rte to 117 taking a left at the intersection noted
Northbound (NB All) - traffic moving across Lincoln Rd towards 126
Southbound (SB All) - traffic moving across Lincoln Rd towards 117
Example Intersection (Lincoln Rd and Codman Rd)
Existing Conditions
2030 Build-out 100%
Volume to Capacity Ratio (V/C) - a value over 1.0 means the intersection is "saturated"
Average Delay (in seconds per vehicle)
Level-of-service (LOS) - A through F as explained above
Queue (in ft) assuming 25 ft per vehicle
Recommendations
(from Ron Muller Associates)
It is recommended that the number of unsignalized, mid-block crosswalks along Lincoln Road be consolidated.
It is recommended that proper pedestrian crossing warning signs be placed at all remaining crossings (W11-2 with W16-7P arrow plaques) as well as appropriate handicap-accessible wheelchair ramps.
It is further recommended that Rectangular Rapid Flashing Beacons (RRFB) be installed at all remaining crossings, as also shown on Figure 12.
It is recommended that the Lincoln Road and Codman Road intersection be closely monitored in the future including calculation of actual vehicle delays and accident experience and that corrective measures be considered if the monitoring shows unacceptable traffic delays or increased accident experience. Such measures could include installation of flashing beacons to advise motorists of the intersecting streets (if delays are acceptable, but an increase in traffic crashes is observed) or traffic capacity improvements such as roundabout traffic control or traffic signal installation. Based on the projected 2030 volumes, the warrants for traffic signal installation are not expected to be met.
Open Questions from the Public
How many additional trips did this study assume based on the 274 additional residential units built at Cold Brook crossing coming through Lincoln Rd both EB and WB?
What factor was used to decrease the number of trips due to internal capture? Did it assume any specifics regarding the number and variety of commercial businesses in this area?
How was LUC 820 used vs LUC 220 used in both 60% and 100% scenarios? Which assume more trips versus the other?
How exactly was the impact of the train crossing factored into the model? While it is referenced, it is not clear if the model shows delays due to this intersection?
How many cars are assumed each unit would have in the model?
Doesn’t the number of new trips per hour (107) seem a bit low given the number of cars that 274 units * 1.5 cars per unit (> 400 cars) would likely have?
Given 70% of the traffic volume is expected to be to/from Rt 2/School area, why did we not study the 5 corners intersection?
Why is there such a huge range (10 to 76) in the net new number of vehicles and how can we reconcile these low figures with the fact that likely 274 units *1.5 cars per unit (>400 cars) will be added under 100% scenario?
What would be the average total time through these intersections, including over the train tracks, for a vehicle during weekday AM and PM currently and under 100% buildout conditions?
How exactly is the impact of TOD factored into the model? What % of residents will take the train and which trips will that replace?
Why was MMLOS (Multi-modal Level of Service) not evaluated when clearly this area has a lot of bicycle and pedestrian traffic in addition to vehicular traffic?
Which type of mitigation would have the biggest impact at Lincoln Rd/Codman Rd for multi-modal use (4 way stop, traffic light, or rotary)?
If the current situation at Lincoln Rd and Codman Rd already receives an “F” grade, why not already implementing a traffic signal at that intersection? I believe the answer is due to the public safety (fire and police) not wanting traffic in front of their driveway which makes sense
Do we think any of these intersections would turn to "F", especially enter/exiting to Lincoln Rd from NB or SB if
a) 450 units were added (as in Option C) with curb cuts mainly on Lincoln Rd?
b) Train frequency was increased?
Special Note for Further Discussion:
Multi-modal Level of Service (LOS)
Multi-modal LOS is a more modern approach to calculating LOS. It was not used in this study.
It is important to understand that LOS is a measure specific to vehicles and does not account for other modes of transportation, namely pedestrians and bicycles.
The 2010 HCM (Highway Capacity Manual) incorporates tools for multimodal analysis of urban streets to encourage users to consider the needs of all travelers. Stand-alone chapters for the bicycle, pedestrian, and transit have been eliminated, and methods applicable to them have been incorporated into the analyses of the various roadway facilities.
The primary basis for the new multimodal procedures is NCHRP Report 616: Multimodal Level of Service Analysis for Urban Streets. This research developed and calibrated a method for evaluating the multimodal LOS (MMLOS) provided by different urban street designs and operations.
This method is designed for evaluating “complete streets,” context-sensitive design alternatives, and smart growth from the perspective of all users of the street.
It is used to evaluate the tradeoffs of various street designs in terms of their effects on the perception of auto drivers, transit passengers, bicyclists, and pedestrians of the quality of service provided by the street.
Multi-Modal LOS Case Study Introduction_USDOT.pdf