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Head-on crash and rollover on the Jamaicaway
By adamg on Thu, 08/17/2017 - 9:35am
Ben Walsh happened upon a head-on crash on the Jamaicaway outbound near Bynner Street shortly before 6 a.m. NBC Boston reports at least one person was taken to the hospital.
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Comments
How does this happen at 25mph
How does this happen at 25mph?
Lol, 25 MPH. I think the
Lol, 25 MPH. I think the average speed on this stretch of road is 40.
Assuming you're serious
And not just lol/trolling, even if the two vehicles were only doing 25, the crash is more like a 50-mph collision because they hit head on.
Do the math...
Crashing head on to an identical vehicle, both moving at 25 mph is not like a 50 mph crash, it is exactly the same as crashing into an immovable barrier at 25 mph.
Thought experiment:
#1: Draw a line in the pavement and crash Car A into Car B exactly at the line. (both moving at 25 mph). No part of either car A or car B crosses the line. The two front bumpers end up exactly at the line; the two rear bumpers end up somewhat back from the line by, I dunno, 3/4 the length of a car.
#2: Replace the line with a screen of tissue paper. Nothing changes -- no part of car A or B penetrates the tissue paper. Any part of car A that tries to penetrate the tissue paper will be met by the identical part of car B, moving towards it at exactly the same speed as the part of car A, and meeting at exactly the tissue paper, and so will stop exactly at the line.
#3: Replace the tissue paper with an immovable steel barricade. Again, nothing changes.
With that said, 25 mph into an immovable barrier is an extremely serious crash.
Wrong--they are not the same
The closing speed in the head on crash is 2v while the closing speed in the first crash is v. There is twice the amount of kinetic energy with the 2 car crash than the single car crash into an immovable object. Dissipating twice the energy will cause greater damage.
That said, in theory in the real world it would be less destructive than a crash at 50 mph into an immovable object. The whole issue is the relativity principle of Newtonian physics. The existence of the road itself would change the dissipation of the kinetic energy. If you placed everything in a vacuum on a frictionless plane it would remove those variables, but I don't know how the tires would generate enough friction to get the cars moving forward at 25 MPH.
Additionally, there would be variables if either of the cars were accelerating at the time of impact but let's try and keep this simple for the kids.
Decelleration
You are decelerating twice the mass.
Of course
That's why I referenced the kinetic energy. Mass is one of the two variables in calculating kinetic energy (the other being velocity).
Of course we must presume the mass is not rotating because that changes the formula. I highly doubt the entire car itself would be rotating in the hypothetical accident unless it was on a frictionless plane.
It's been a while since HS physics
It's been a while since HS physics and I welcome clarification, but I think you are missing that two objects in motion that collide will both experience an instantaneous deceleration from 25mph to 0mph, so would not the force (=ma) be much greater than in a collision with an object of the same mass at rest?
Unlike falling....
It's not (just) the sudden stop that kills you; it is the energy being dissipated. As an earlier poster noted, it's not exactly 2x, but its closer to 2x than 1x.
To tweak your earlier example, place a piece of aluminium between a vehicle and an immovable object, and crash the vehicle at 25mph.
Now take the same piece of aluminium and and place it between 2 cars as they crash into each other. In the latter, the metal will be more compacted.
Finally, because this is Boston, have David Ortiz square up perfectly on a baseball set on a T-Ball stand, and then have him connect identically on a 100mph Kimbrall fastball. The former is in the first row of the Monster seats and the latter is somewhere out on the Pike.
Wait...what?
Try this thought experiment: lay one hand on your desk palm up, and slap your other palm against it at the international standard velocity used for clapping.
Now take your hand off the desk, reattach it if necessary, and bring both hands together at the same speed as above.
Now stand up. If other people are clapping, take a bow. You earned it!
Hope all involved
End up ok.
It's shocking this doesn't happen more often on the J Way.
It does happen more often - I
It does happen more often - I've lived at this intersection for less than a year and I've seen 2 cars flipped on Bynner, and countless accidents at this intersection - not to mention the never ending car horns from people.
This intersection is dangerous and people drive like lunatics at all hours of the day
If Boston & DCR were #VisionZero
http://www.bostoncompletestreets.org/pdf/2013/4_6_IntersectionGeometry.pdf
Perhaps you are unaware?
The Jamaicaway has lights at the intersections so raised crossings are not needed.
huh?
how does a traffic light encourage drivers to slow down when the light is green?
Shut the Jamiacaway down to
Shut the Jamiacaway down to traffic. Set it up for trolley cars and express buses only. Drivers have proven many times they can't be trusted to operate on it. The parks and Jamaica pond will be much more pleasant without 4 lanes of traffic going by.
How do you propose to get
How do you propose to get people that drive up from the southern regions of Boston and parts beyond into or north of the city?
Many of whom are heading to the Longwood Medical area.
n/t
There are plenty of lovely highways they may use
Where they may speed without risk to vulnerable road users.
Too Narrow
The JWay is obscenely narrow for 4 lanes of moderate to heavy traffic.
it is the same as Mem Dr in Cambridgeport
both are ~40' wide
Not the same
The Jway is not only narrow but also winding and hilly. A head-on is a constant possibility. And, stopping to take a left at the light at Bynner St. always feels like an accident waiting to happen.
I avoid this road as much as possible, especially with today's distracted drivers.
width is the same, roadway design is different
you are right - a 40' wide 4 lane road can be more or less safe depending on how it is designed
The Jway would work better if
The Jway would work better if they could build a medium.
A medium?
Yeah, it might be useful if you were screaming along at 60mph and someone could predict that there was oncoming traffic.
No, like in a séance
A medium to talk to ghosts. Jamaica Way drivers could listen to that in podcast form. It'd make the drive a lot more interesting.
The NBC page had text
The NBC page had text describing this accident but the accompanying video was for a rental truck rollover on some 4 lane highway (93?). The sign was too blurry to read.
We were overdue for another one
A road on which head-on collisions happen with such terrifying regularity is just unsafe by definition.
A posted speed limit which is ignored by literally everyone is (also by definition!) an ineffective safety measure.
They need to either widen the road or get rid of a lane. Why the status quo is tolerable to the city is beyond me.
DCR
It's a DCR road. Write to your State rep. and senator, and lobby them for change, and ask them to budget funds enough that the DCR has enough money to do their job. Improvements are slow or are not happening because the DCR's budget has been cut by about 30% during the past 10 years.
It's the State that accepts this status quo.
Better yet
Let DCR do their parkland thing and let DOT handle the highways.
Agreed...
Let's stop treating our parkways like highways. That's what you meant, right?
It is so dumb that DCR owns
It is so dumb that DCR owns these roads. Either give them to the various cities or loop them in under DOT. Duplicating staffing and work and contracts for essentially the same types of work between two separate agencies, one of which is not in the road business, is the definition of government inefficiency. Plus, DCR takes terrible care of them when it's snowing.
Ignored
Yes, no one travels at 25 mph on the JW. I always drive in the right lane which feels a little safer. I'm pretty certain the lanes are narrower than current road standards so combined with the hills and curves, driving in the center lane always feels risky. Oncoming cars pass inches away with little room for error.
There's really no good solution other than cracking down and being vigilant on anyone going over 25 mph. Widening the JW is almost impossible - it would require taking down 100s of mature trees and encroaching on the park and private property. NIMBYs and treehuggers would be in an uproar.
Much cheaper to station police at several spots with and ticket drivers until they get the point.