ROAD SAFETY AUDIT TRUCK ROLLOVER CRASHES

Transcription

1 ROAD SAFETY AUDIT TRUCK ROLLOVER CRASHES I-95/I-495 Interchange Town of Foxborough Town of Mansfield December 28, 2012 Prepared For: MassDOT Highway Division Prepared By: BETA Group, Inc.

2 Table of Contents Project Data...1 Background...2 Project Description...2 Audit Observations...6 Potential Safety Enhancements...10 Summary of Road Safety Audit...13 List of Appendices Appendix A. Appendix B. Appendix C. Appendix D. RSA Meeting Agenda RSA Audit Team Contact List Crash Diagram Traffic Volume Data List of Figures Figure 1. Location Map... 3 List of Tables Table 1. Table 2. Table 3. Table 4. Participating Audit Team Members... 1 Ramp Traffic Data... 5 Estimated Time Frame and Costs Breakdown Potential Safety Enhancement Summary... 14

3 Project Data A Road Safety Audit for Truck Rollover Crashes at the interchange of Interstate 95 (I-95) and Interstate 495 (I-495) in Foxborough and Mansfield was held on November 28, 2012 at the Foxborough Fire Station in Foxborough, MA. As indicated in Table 1, the audit team consisted of representatives from Federal, State, Regional and Local agencies and included a cross-section of engineering, planning, operations, safety, enforcement and emergency response expertise. Table 1. Participating Audit Team Members Audit Team Member Bonnie Polin Corey O Connor Neil Boudreau Steve Timmins Edward Feeney Barbara LaChance Thomas Burnett Matthew Poirier Jeff Stuart Paul D Amore Roger Hatfield Steve Bagley Robin Riessman Neal Boldrighini Greg Lucas Justin Curewitz Agency/Affiliation MassDOT Highway Division Safety MassDOT Highway Division Safety MassDOT Highway Division State Traffic Engineer MassDOT Highway Division Traffic MassDOT Highway Division District 5 Traffic Operations MassDOT Highway Division District 5 Traffic Operations MassDOT Highway Division Safety Section FMCSA USDOT Massachusetts State Police Foxboro Massachusetts State Police Troop H HQ Foxborough Fire Dept Chief Foxborough Fire Dept. Deputy Chief UMass Safe Mansfield Fire Dept. Chief BETA Group, Inc. BETA Group, Inc. Page 1

4 Background The Federal Highway Administration defines a Road Safety Audit (RSA) as the formal safety examination of an existing or future road or intersection by an independent, multidisciplinary team. The purpose of an RSA is to identify potential safety issues and possible opportunities for safety improvements considering all roadway users. A Road Safety Audit was scheduled for the I-95 and I-495 interchange because it has been identified as a high crash location for truck crashes including rollovers. The interchange is a full cloverleaf and the audit included all eight ramps that form the interchange between the two highways. The purpose of the RSA is to identify both short and long term safety improvements that can be implemented to reduce crashes at the interchange. Project Description The interchange of Interstates 95 and 495, shown in Figure 1, is bisected by the town line separating Foxborough and Mansfield. The interchange is a full cloverleaf interchange with separate ramps for each connection in each direction between the two highways. The ramps from I-95 Northbound to I-495 Northbound, I-95 Southbound to I-495 Southbound, I-495 Northbound to I-95 Southbound and I-495 Southbound to I-95 Northbound are loop ramps, while the ramps from I-95 Northbound to I-495 Southbound, I-95 Southbound to I-495 Northbound, I-495 Northbound to I-95 Northbound and I-495 Southbound to I-95 Southbound are typically composed of an entry curve to the right, a short tangent segment, a curve to the left, another short tangent segment and a final curve to the right to merge onto the mainline. I-495 is approximately 120 miles in length and serves as the outer loop around the greater Boston area, extending essentially from Cape Cod to the New Hampshire border. I-495 is a north-south route but follows more of an east-west alignment at its interchange with I-95, as can be seen in Figure 1. Both highways are highly desirable corridors for both local and regional truck travel. Truck crash data for the interchange were provided by the Massachusetts State Police from 2008 to the present. The crash summary diagram included in the Appendix shows 19 total crashes on the ramps or at the entry or exit to the ramps between I-95 and I-495. One additional truck rollover crash occurred in the week following the audit on the ramp from I-95 Northbound to I-495 Southbound. A discussion of crash details by ramp follows. I-95 Northbound to I-495 Southbound This ramp experienced five crashes: a rear-end crash; a merge related crash; a crossover crash; and two rollover crashes. The rear-end crash involved a truck rear-ending a passenger car and occurred at the entry to the ramp. The merge related crash also occurred at the entry to the ramp and involved a vehicle beginning to exit then merging back into the I-95 travel lane and colliding with a truck. The crossover crash involved a car on the loop ramp from I-495 Southbound to I-95 Northbound which left the ramp, crossed over to the I-95 Northbound to I-495 Southbound ramp and struck a truck. Page 2

5 INTERSTATE 495 NORTH INTERSTATE 495 SOUTH FOXBOROUGH MANSFIELD INTERSTATE INTERSTATE 95 NORTH 95 SOUTH INTERSTATE 95 SOUTH INTERSTATE 495 NORTH INTERSTATE 495 SOUTH INTERSTATE 95 NORTH LEGEND TOWN LINE Road Safety Audit I-95/I-495 Interchange Foxborough/Mansfield, MA Figure 1 Location Map

6 The two truck rollover crashes, including the most recent crash which is not shown on the diagram, occurred near the end of the ramp at the merge to I-495 Southbound. Rollover crashes occur when a load shift causes the trailer wheels to lift. Momentum carries the trailer over and brings the truck cab with it. This shift occurs due to excessive speed; either the driver is carrying too much speed through the ramp, or the driver is accelerating at the end of the ramp in anticipation of merging into traffic on I-495. A single W1-13 Truck Rollover sign with a 25 MPH advisory plaque is located on the left side at the entrance to the ramp, but no additional signs are provided at the curve where the two rollover crashes occurred. I-495 Southbound to I-95 Northbound This loop ramp experienced three crashes in the study period: a rear-end crash, the previously discussed crossover crash, and a truck rollover crash. The rear-end crash occurred at the entry to the ramp when a truck rear-ended a car. Driver inattention was cited as a cause. The rollover crash occurred near the end of the compound curve. No rollover warning signs are posted on the ramp. I-95 Southbound to I-495 Northbound This ramp experienced two crashes in the study period: a rollover crash that did not involve a truck and a merge related crash at the end of the ramp. The rollover crash involved a school van that lost control in wet conditions, struck the curb, left the road and rolled over. The merge related crash also occurred in wet conditions and involved a vehicle skidding across the ramp into the travel lane, where it struck a truck. A W1-13 Truck Rollover sign with 25 MPH supplemental plaque is located on the left side at the entrance to the ramp, and a second rollover sign is located at the beginning of the curve to the right at the end of the ramp. W1-8 Chevron arrows are included for the curve to the left in the middle of the ramp and the curve to the right at the end of the ramp. I-495 Northbound to I-95 Southbound This loop ramp experienced two truck rollover crashes and one single vehicle truck crash in the study period. Two rollover crashes occurred in the loop near the end of the compound curve. Speed was cited as a direct factor in one crash, and may have been a factor in the second crash which involved a truck striking the curb and then losing control and rolling over. The single vehicle truck crash occurred at the end of the ramp where a truck struck the guardrail at the end of the ramp protecting the bridge abutment. No rollover warning signs are posted on the ramp. I-495 Northbound to I-95 Northbound This ramp experienced one rear-end crash and two crossover crashes in the study period. The rear-end crash occurred at the entry to the ramp and involving a car stopping short and being struck by a truck. The crossover crashes involved a car on the loop ramp from I-95 Northbound to I-495 Northbound which left the ramp, crossed over to the I-495 Northbound to I-95 Northbound ramp and hit a truck. One of the crashes involved contact with a tractor trailer, while the other involved a light truck. No truck rollover crashes occurred on this ramp. Page 4

7 I-95 Northbound to I-495 Northbound This loop ramp experienced three crashes in the study period: the two previously discussed crossover crashes and a merge related crash. The merge related crash occurred at the end of the ramp and was a chain reaction crash in which a truck almost hit a car, which then swerved, causing another truck to swerve to the left and strike another car. A rollover warning sign with a 25 MPH advisory plaque is located on the left side at the entrance to the ramp. I-495 Southbound to I-95 Southbound This ramp experienced two rollover crashes in the study period. One rollover crash occurred at the entry to the ramp when the driver was late in entering the turn and overturned the vehicle. The second crash occurred near the end of the ramp; speed was cited as a factor. No rollover warning signs are posted on the ramp. I-95 Southbound to I-495 Southbound This loop ramp experienced one rollover crash and one rear-end crash in the study period. The rollover crash involved a vehicle that stopped short, causing a truck operator to brake hard and lose control of the vehicle, which then overturned. The truck driver was cited for speeding. The rear-end crash occurred at the end of the ramp when a truck was rear-ended by a car during construction when the breakdown lane was in use as a travel lane. No rollover warning signs are posted on the ramp. Automatic Traffic Recorder (ATR) data collected in February of 2012 were made available to audit participants. The data is summarized in Table 2 and included in the Appendix. Table 2. Ramp Traffic Data Ramp 2012 ADT T ph T ad I-95 NB to I-495 SB 10,800 6% 8% I-495 SB to I-95 NB 10,200 4% 5% I-95 SB to I-495 NB 19,500 4% 9% I-495 NB to I-95 SB 12,200 2% 6% I-495 NB to I-95 NB 7,100 2% 5% I-95 NB to I-495 NB 11,300 1% 5% I-495 SB to I-95 SB 11,400 3% 6% I-95 SB to I-495 SB 7,000 1% 4% ADT: Average Daily Traffic T ph : Truck Percentage, Peak Hour of Traffic T ad : Truck Percentage, All Day Traffic. Page 5

8 Audit Observations Following a brief introduction to the RSA process, the audit participants were asked to discuss safety issues and other factors that lead to the occurrence of truck crashes including rollover crashes at the I- 95/I-495 interchange. Audit participants were presented with crash information, viewed a video recording of each ramp, and noted safety issues and contributing factors both during and following the video. A summary of the issues common to all ramps is included, followed by a summary of issues that relate to a specific ramp only. Exit/Ramp Signage It was noted that current MassDOT standard practice when signing ramps is to provide both W13-2 EXIT XX MPH and W13-3 RAMP XX MPH advisory speed signs. Existing ramp speed signage is inconsistent; only three out of the eight ramps have both exit and ramp speed signage, and the I-95 Southbound to I-495 Northbound ramp displays different speeds for each. Ramp Delineation - In-pavement reflectors are not provided along any of the study ramps. Reflectors would help delineate the ramp for nighttime travel. Delineator posts are also not provided along the study ramps. It was noted that delineator posts may help prevent crossover crashes by providing additional guidance at night and increasing driver awareness of the ramp edge and the curbed area between the loop ramp and the outside ramp. Rollover Signage Existing rollover signage is Lack of Delineation inconsistent and is typically not repeated at the final I-95 NB to I-495 NB curve near the end of the ramp, where the majority of rollover crashes occur. Inadequate Acceleration Lane Length It was suggested that the history of merge crashes and/or rearend crashes at the end of the ramps is a result of inadequate room for driver acceleration, and that drivers feel the need to quickly accelerate to merge into the travel lane. This is especially true of the I- 95 Southbound to I-495 Northbound ramp, where a rollover crash and a merge related crash at the end of the ramp were attributed to speed under wet road conditions. It was noted that the existing bridge structure carrying I-495 over I-95 limits the ability to extend acceleration lane length between the loop ramps on both highways. Weaving - I-95 and I-495 both provide a weaving lane between the entering loop ramp and the exiting loop ramp. This lane is not delineated in either direction on either highway, resulting in no defined separation between the weaving lane and the inside travel lane. I-95 Northbound to I-495 Southbound Rollover Signage A rollover sign is located at the entry to the ramp, with no additional rollover signs or chevron arrows. One rollover crash occurred near the end of the ramp. Page 6

9 I-495 Southbound to I-95 Northbound Rollover Signage No rollover or chevron signage is provided on this ramp, where one rollover crash and one crossover crash occurred. Diesel Fuel It was noted that the ramp may become slick from excess diesel fuel that spills on the ramp from trucks that recently refueled in Plainville. I-95 Southbound to I-495 Northbound Ramp Speed Signage This ramp has an Exit advisory speed sign with a 30 MPH limit and a Ramp advisory speed sign with a 25 MPH limit. These signs are too closely spaced, which presents confusion and may cause drivers to enter the ramp at an unsafe speed. Rollover Signage Although this ramp provides two rollover signs, no supplemental speed plaque is provided on the rollover sign located at the entrance to the final curve, where the rollover crash involving a school van occurred. Chevron arrows are provided for the middle curve to the left and the final curve to the right, although it appears that some are missing from the final curve. Pavement Condition Worn pavement can have a Rollover and Chevron Signage lower friction coefficient which can be related to an increased risk of rollover crashes, especially under wet conditions. The rollover crash and a merge related crash both occurred under wet conditions. It is unknown when the ramp and the merge area with I-495 were last resurfaced. Merge Signage It was noted that deficiencies may exist in merge signage due to the two crashes involving vehicle speed near the end of the ramp. Existing merge signage consists of a typical W4-1R Merge sign on the I-495 mainline in advance on the ramp merge. Previously stated deficiencies in acceleration lane length are also a potential contributing factor in merge-related crashes. I-495 Northbound to I-95 Southbound Rollover Signage No rollover signage is provided on this ramp, where one rollover crash and one crossover crash occurred. Four chevron signs are located in the middle of the ramp loop, but are lacking from the beginning and end of the ramp where the curvature is greatest. The lack of chevron signs was specifically noted as a safety concern. Weaving The existing geometry of the interchange provides a short weaving area between exiting traffic and traffic entering the ramp from I-95 Southbound to I-495 Southbound. It is in this area that a truck hit the guardrail, although it should be noted that inattention was cited as a factor in that crash. Page 7

10 I-495 Northbound to I-95 Northbound Rollover Signage No rollover signage is provided on this ramp, although no rollover crashes occurred on this ramp. Two crossover crashes left the adjacent loop ramp and struck vehicles on this ramp. I-95 Northbound to I-495 Northbound Rollover Signage A rollover sign is located at the entry to the ramp, with no additional rollover signs or chevron arrows. Two crossover crashes occurred on the ramp. Guide Sign The last in a series of advance guide signs for an interchange is the Exit Direction sign, confirming the destination, location and direction of the exit. This sign is typically located at the beginning of a deceleration lane or at the beginning of the ramp gore. Due to the overhead bridge structure carrying I-495 over I-95, two Exit Direction signs are located at this ramp one on the bridge structure, and one ground mounted to the right of the ramp entry following the bridge structure. It was noted that this ground mounted sign is not clearly visible and in fact blocks visibility of the ramp speed advisory sign and the rollover warning sign. Stormwater Flow It was noted that water flows across the ramp during rain events, which reduces pavement friction and can cause vehicles to hydroplane. I-495 Southbound to I-95 Southbound Ramp Speed Signage This ramp has a Ramp advisory speed sign with a 30 MPH limit. It was suggested that this advisory speed limit is too high for the ramp geometry. Rollover Signage No rollover signage is provided on this ramp, where one rollover crash occurred. Traffic Congestion It was noted that traffic slows down and sometimes backs up on I-95 Southbound south of I-495, which can impact operations of the ramp. No crashes related to merging involving trucks were identified for this ramp. Page 8

11 I-95 Southbound to I-495 Southbound Guide Sign The ground mounted Exit Direction sign for this exit is missing. It was noted that the ground mounted exit direction signs for the loop ramps to I-495 from I-95 were relocated to the exit gore during a bridge construction project, and then were to be relocated back to their original ground mounted location on the right side following construction. It was theorized that the sign at this location was not relocated following construction. Mile Marker Sign The existing ramp speed advisory sign is partially blocked by a mile marker sign, as can be seen in the above picture. Rollover Signage No rollover signage is provided on this ramp. A rollover crash occurred at the entry to the ramp, but may have been due to another motorist and not related to the ramp geometry. Page 9

12 Potential Safety Enhancements Audit participants identified safety issues and recommended potential improvements to address these issues. These improvements are intended to reduce the number of rollover crashes, reduce the severity of all crashes and increase the overall safety of the I-95/I-495 interchange. Specific recommendations are discussed in detail in this section and summarized in Table 3. Each improvement considered has been categorized as short-term, mid-term, or long-term based on the definitions shown in Table 2. Additionally, a cost category has been assigned to each improvement based on the parameters set forth in Table 2. Table 3. Estimated Time Frame and Costs Breakdown Time Frame Costs Short-term <1 year Low <$10,000 Mid-term 1 3 years Medium $10,000 $50,000 Long-term >3 years High >$50,000 Update Exit and Ramp advisory speed signage to be consistent with current MassDOT practice. New EXIT 25 MPH signs should be placed at or immediately prior to the overhead exit direction sign, while the RAMP 25 MPH sign should be placed on the right side of the ramp at the end of the paved gore. Combined ramp alignment/advisory speed signs as shown at right should be used for the loop ramps. This is a short-term, low cost improvement. Proposed W13-2 EXIT 25 MPH and W13-3 RAMP 25 MPH signs should be 60 x48, while the combined ramp alignment/advisory speed signs (W13-6 and W13-7) should be 72 x48. All signs should use fluorescent high intensity yellow aluminum sheeting. All new signs should display 25 MPH, which addresses the existing discrepancy at the I-95 Southbound to I-495 Northbound ramp, and reduces the ramp advisory speed for the I-495 Southbound to I-95 Southbound ramp. All existing ramp advisory speed signs should be removed. Update truck rollover signs for ramps where rollover or crossover crashes have occurred. This is true of the following ramps: o o o o o o I-95 Northbound to I-495 Southbound I-495 Southbound to I-95 Northbound (loop) I-95 Southbound to I-495 Northbound I-495 Northbound to I-95 Southbound (loop) I-95 Northbound to I-495 Northbound (loop) I-495 Southbound to I-95 Southbound All ramps identified above should have new 48 x48 W13-1 Truck Rollover signs with a 25 MPH supplemental plaque. The outside (non-loop) ramps should have an additional rollover sign with supplemental plaque at the beginning of the final curve to the right at the end of the ramp, where the threat of rollover is greatest. This is a short-term, low cost improvement. All signs should use Page 10

13 fluorescent high intensity yellow aluminum sheeting. All existing truck rollover signs should be removed. Provide new 42 x48 W1-8 Chevron signs for all ramps where truck rollover signage is to be updated. Chevron arrows should be placed along all curves on the ramp, and all existing chevron signage should be removed. Signs should have a fluorescent high intensity yellow background. Exact quantities and locations of chevron signs should be determined by MassDOT. This is a short-term, low cost improvement. Replace H1-2 warning cluster panels in the exit ramp gores with larger 36 x36 signs, which is the current MassDOT standard for Interstate highway exit gores. Existing H1-2 panels are 24 x24. This is a short-term, low cost improvement. Provide yellow delineator posts along the curbed area between the outside ramps and loop ramps on all four quadrants of the interchange. This improvement will increase visibility at night, which may reduce the likelihood of crossover crashes. This is a short-term, low cost improvement. Delineator posts should be installed in sleeves, which will facilitate maintenance if they are knocked down. Investigate pavement condition for all ramps. It is unknown when ramps were last resurfaced. If resurfacing is necessary, high friction pavement should be considered. It was noted during a previous truck rollover RSA at the I-95/I-295 intersection in Attleboro that the state of Kansas has reported success with high friction pavements in high rollover crash locations. This type of pavement should be researched to determine its feasibility at the I-95/I-495 interchange. Increased pavement friction could help keep the truck s tires on the pavement and in turn prevent tipping and rollovers. This is a mid-term, high cost improvement that requires additional study. Install in-pavement reflectors along all ramps at the interchange. MassDOT has installed recessed, inpavement reflectors, also known as pavement markers, along many miles of highway throughout the Commonwealth. These reflectors should be installed along all ramps at the I-95/I-495 interchange to increase visibility and awareness of the ramp geometry at night. This is a short-term, medium cost improvement. An evaluation of pavement condition described above should precede installation of pavement markers. If ramps require resurfacing, pavement markers can be installed at the same time as the resurfacing. If the pavement condition is generally good, but the pavement is deemed to be too old for the installation of recessed markers, consideration should be given to installing raised markers located just outside of the edge line. Investigate the feasibility of providing acceleration lanes at the end of all four outer ramps. Under current conditions, drivers are known to accelerate while still navigating the ramp in order to reach their desired speed for merging into free flow traffic along the mainline. Providing adequate acceleration lanes would allow the driver to remain at an appropriate speed for the ramp and then use the acceleration lane to accelerate to merging speed. This is a long-term, high cost improvement. Provide new pavement markings for weaving lanes consistent with Figure 3B-10 of the Manual on Uniform Traffic Control Devices. This will provide delineation of the weaving lane where none exists Page 11

14 today. This is a short-term, low cost improvement that should be applied to the weaving lane between the two loop ramps in both directions on both I-95 and I-495. Investigate merge crashes involving all vehicles on the I-95 Southbound to I-495 Northbound ramp. Two crashes occurred on this ramp that involved vehicle speed on a wet roadway surface at the top of the ramp. If the ramp merge shows a significant history of merge-related crashes involving all vehicles, additional signage or geometric modifications should be considered. If the crash history includes a high percentage of crashes in wet weather conditions, drainage improvements may be necessary. This is a short-term, low cost improvement that may trigger other long-term improvements. Remove the ground mounted guide sign for the I-95 Northbound to I-495 Northbound ramp and replace it with a new sign in the exit gore, and provide a guide sign in the exit gore for the I-95 Southbound to I-495 Southbound ramp. It was noted that the existing sign on the I-95 Northbound to I-495 Northbound ramp blocks visibility of other existing signage and is not clearly visible due to the proximity of the bridge structure. The missing sign on the I-95 Southbound to I-495 Southbound ramp should be replaced and mounted in the exit gore. Installing new signs at both locations will insure a consistent appearance in signage. These signs will replace the existing exit gore signs, which should be removed. The existing memorial at the base of the existing sign on the I-95 Northbound to I-495 Northbound ramp should be relocated to the base of the new sign in the exit gore. It was noted that while placing guide signs in the exit gore is atypical and not consistent with other exit gore signage along I-95, it is acceptable for an Interstate to Interstate connection. This is a short-term, medium cost improvement. Relocate the mile marker sign for the I-95 Northbound to I-495 Northbound ramp. The location of the relocated sign should be considered relative to other signage recommendations. This is a short-term, low cost improvement. Investigate stormwater flow along the I-95 Northbound to I-495 Northbound ramp. Existing catch basins are provided on the right side of this ramp, but it was suggested that water sheet flow extends beyond these basins across the ramp. It should be determined if existing drainage is adequate for the ramp geometry. This is a short-term, low cost improvement. Study the crash history of the I-495 Southbound to I-95 Southbound ramp due to concerns over traffic congestion. If the ramp shows a significant history of rear-end crashes involving all vehicles, signage or geometric modifications should be considered. This is a short-term, low cost improvement. Consider rollover hazard advisory signs on both I-95 and I-495 prior to the I-95/I-495 interchange. These panels would be similar to signs currently in place on I-93 prior to the I-95/Rt. 128 interchange in Woburn, pictured at right. Rollover advisory signs would be a short-term, medium cost improvement. Page 12

15 Summary of Road Safety Audit Table 3 summarizes potential recommendations discussed by the audit team. The recommendations are categorized based on the potential safety payoff, as well as by time frame and cost. The safety payoff is a qualitative judgment of the effectiveness of the potential safety improvements. The cost is a preliminary order of magnitude estimate based on prior experience with roadway and safety improvements. Cost does not include inflation or construction administration. Page 13

16 Table 4. Potential Safety Enhancement Summary Safety Issue Safety Enhancement Safety Payoff Responsibility Time Frame Cost Exit/Ramp Signage Rollover Signage Rollover Signage Ramp Delineation Pavement Condition Ramp Delineation Inadequate Acceleration Lane Length Weaving Merge Signage Guide Sign Mile Marker Signage Update Exit and Ramp advisory speed signage to be consistent with current MassDOT practice. Update truck rollover signs for ramps where rollover or crossover crashes have occurred. Provide new 42 x48 W1-8 Chevron signs for all ramps where truck rollover signage is to be updated. Provide yellow delineator posts along the curbed area between the outside ramps and loop ramps on all four quadrants of the interchange. Posts should be installed in sleeves to facilitate maintenance. Investigate pavement condition for all ramps. Determine when last resurfacing took place, and consider high friction pavement if resurfacing is necessary. Install in-pavement reflectors (pavement markers) along all ramps at the interchange. An evaluation of pavement condition should precede installation of pavement markers. Investigate the feasibility of providing acceleration lanes at the end of all four outer loop ramps. Provide new pavement markings for weaving lanes consistent with Figure 3B-10 of the Manual on Uniform Traffic Control Devices Investigate merge crashes involving all vehicles on the I-95 SB to I-495 NB ramp, and consider signage updates or geometric modifications if warranted. Remove the existing ground mounted guide sign for the I-95 NB to I-495 NB ramp and replace it with a new sign in the exit gore (include relocated memorial). Provide a new ground mounted guide sign for the I-95 SB to I-495 SB ramp in the exit gore. Relocate the mile marker sign at the I-95 NB to I-495 NB ramp. The location of the relocated sign should be considered relative to other signage recommendations. Medium MassDOT Short-term $6,500 High MassDOT Short-term $3,000 High MassDOT Short-term $10,000 High MassDOT Short-term $5,000 High MassDOT Mid-term TBD High MassDOT Short-term $25,000 High MassDOT Long-term TBD Medium MassDOT Short-term $5,000 High MassDOT Short-term (Study) TBD Medium MassDOT Short-term $6,000 Medium MassDOT Short-term $500 Page 14

17 Table 4. Potential Safety Enhancement Summary Safety Issue Safety Enhancement Safety Payoff Responsibility Time Frame Cost Stormwater Flow Investigate stormwater flow along the I-95 NB to I-495 NB ramp. Medium MassDOT Short-term TBD Traffic Congestion Rollover Signage Study the crash history of the I-495 SB to I-95 SB ramp due to concerns over traffic congestion. Consider rollover hazard advisory signs on both I-95 and I-495 similar to those installed on I-93 in Woburn. Medium MassDOT Short-term TBD Medium MassDOT Short-term $15,000 Page 15

18 Appendix A. RSA Meeting Agenda

19 Appendix B. RSA Audit Team Contact List

20 Appendix C. Crash Diagram

21 Legend CrashType e Crossover 0 Merge Related e Rear End N 0 Single Vehicle/Rol love r Q Municipal Boundary --80 ==--==~eel ~7!!!.4lJPQI

22 Appendix D. Traffic Volume Data

23 1. Off-Ramp from I-95 SB to I-495 NB 2012 actual ADT = 19, forecast ADT = 21,500 Tph = 4% Tad = 9% 2. Off-Ramp from I-495 NB to I-95 SB 2012 actual ADT = 12, forecast ADT = 15,600 Tph = 2% Tad = 6% 3. Off-Ramp from I-95 SB to I-495 SB 2012 actual ADT = 7, forecast ADT = 7,600 Tph = 1% Tad = 4% 4. Off-Ramp from I-495 SB to I-95 SB 2012 actual ADT = 11, forecast ADT = 16,400 Tph = 3% Tad = 6% 5. Off-Ramp from I-95 NB to I-495 SB 2012 actual ADT = 10, forecast ADT = 15,100 Tph = 6% Tad = 8% 6. Off-Ramp from I-495 SB to I-95 NB 2012 actual ADT = 10, forecast ADT = 11,700 Tph = 4% Tad = 5% 7. Off-Ramp from I-95 NB to I-495 NB 2012 actual ADT = 11, forecast ADT = 14,200 Tph = 1% Tad = 5% 8. Off-Ramp from I-495 NB to I-95 NB 2012 actual ADT = 7, forecast ADT = 8,300 Tph = 2% Tad = 5%