Serious bike on bike crash. Head on.

Bobsiii

Active Member
Why speed limits on MUPs? Try this.

This sounds like it would have been a lot less serious if the one biker were not going so fast. I ride here often, keep to 14-15 mph and get passed a ton. Hell, an idiot on scooter passed me the other day! I rode here the day after the crash and saw two radar setups, waving cyclists over.

And the point about the infrastructure is dead on.


https://www.denverpost.com/2019/06/26/denver-cherry-creek-bike-crash/?fbclid=IwAR0MxONCCSw1EB59U29vcE56_w9VmuksHnb6wqjVUyyTIYX9l2R3eY6heqw
 

AlanDB

Well-Known Member
Yikes! What a terrible crash! I hope both riders can fully recover. From the story and comments, it doesn't sound like e-bikes were involved, but still, this kind of story does not help the public perception of cyclists and cycling.
 

christob

Well-Known Member
I felt a pang of relief to read there WASN'T an ebike involved... just an old-fashioned collision of pedal-bikes, where the high speed of (at least one rider) was human-powered.
I don't mean at all for that to sound crass; I'm certainly glad both parties live, and can't imagine the pain and injuries you'd take away from a bad crash like that... but I can't deny the small relief reading the details that for once, it wasn't an "ebiker recklessly speeding" that was blamed for the cause, or even involved...

It is a scary reminder of just how fast 'athlete' cyclists can go, while ebikes are routinely focused on for the "speed problem" on trails; I routinely get passed by higher-speed pedal-bikes comfortably doing 20+ (on local MUT's as well as a popular 3 mile stretch of one-way road I ride, where I'm usually at about 15 or 16mph avg.) The commentary on the Denver MUT capacity and design is spot on -- our trails here, too, are frequently very popular with all manner of users, all ages, all modes of movement -- very much at capacity or beyond (not to mention, not wide enough, nor in places, maintained well enough) and yet, not all cyclists or scooter riders, hopefully knowing this as common sense, adjust their ride through the crowded areas accordingly and sensibly, nor seem to obey the posted (granted, not at all easy to spot) MUT speed limit of 15mph.
 

Mr. Coffee

Well-Known Member
We should all keep in mind even with a 15mph speed limit a head-on collision can do the damage that a 30mph collision into a stationary object would do -- which is easily enough damage to send you to the ER.

In addition to enforcement efforts and improving infra, it seems like this trail is a good candidate for adding traffic calming elements like bollards that would make a 15mph limit self-enforcing.
 

Bobsiii

Active Member
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In addition to enforcement efforts and improving infra, it seems like this trail is a good candidate for adding traffic calming elements like bollards that would make a 15mph limit self-enforcing.
I hate the speed racer crowd when they show up on MUTs but despite the role speed played in the severity this crash I don't think it had much to do with causing the accident; I think the extreme multi-modal nature of the traffic on this path and the crowding in the area of the accident - Downtown - have a lot more to do with the problem. I'm not a fan of bumps and bollards, I think the whole metro area needs to figure out how to deal with the changing transportation landscape, with an eye to safe accommodations for all. There is a Regional Council of Governments but I haven't heard anything from them in forever.
 

AlanDB

Well-Known Member
We have probably all seen videos of the masses of people in Asia and Europe riding bikes on very congested bikeways in a very organized, controlled and safe fashion. So we know it is possible. I think proper infrastructure has a lot to do with it, but also riding experience and a culture that promotes respect for everyone using the public facilities.
 

Toomanycats

Active Member
Horrifying. I hope the gentleman makes a full recovery.
I’ve said it before and I’m sorry to be repetitive. It’s not just speed, although that contributes. I’d rather deal with a fast rider that keeps a straight line, has good control of the bike, and knows what they’re doing. It’s the oblivious rider that veers all over the bike lanes (or the little kid not being watched by their parent riding their bike all over the place) the worries me.
That being said, I don’t know why the lady on the beach cruiser went out of the lane. Maybe she was trying to avoid yet another rider, although it sounds like she was riding next to another rider or trying to pass, and they collided.
 

Over50

Well-Known Member
Horrific crash. I can see this happening on my local greenway. Common are the meandering, casual riders who stray around the lanes, have no mirrors, ride multiple abreast. Common as well are the roadies in pairs or groups approaching pedestrians and casual cyclists at speeds easily around 20 mph. Common are the dog walkers, walking in the bike lanes looking at their phones whilst the dogs are running to and fro on their long leashes or even unleashed. Common are the little kids, excited to be out on a summer's day, darting around their parents like squirrels. Common are the youth standing in the bike lanes in front of a mural staging a selfie ... Speed on the MUP in those conditions is not a wise choice.
 

Timpo

Well-Known Member
We should all keep in mind even with a 15mph speed limit a head-on collision can do the damage that a 30mph collision into a stationary object would do -- which is easily enough damage to send you to the ER.

In addition to enforcement efforts and improving infra, it seems like this trail is a good candidate for adding traffic calming elements like bollards that would make a 15mph limit self-enforcing.
sorry but that's not how physics work, there's no difference if you hit a stationary object at 15mph, or if you hit a 15mph cyclist head on while riding at 15mph.

nevertheless, this is very unfortunate that it happened, maybe a good reminder for us to watch out and be careful. Because the reality is, it could have happened to any one of us.
cycling lanes are not the safest thing...it is very narrow, and we have people riding at 10mph or less, or athletes going on roadbike at 30mph..some people are walking at 3mph or jogging at 7 or 8mph.
 

harryS

Well-Known Member
The story is sad. I hope both recover.

Not to cheapen the thread, but there's a diff between hitting a wall at 15 mph and you and another cyclist hitting each other at 15 mph. Just calculate the energy. You hit that wall, you dissipate all your energy. Two of you hit each other, kaboom, twice as much energy.
 

christob

Well-Known Member
It will probably diverge the thread, but two objects of same mass, colliding with each other head-on while traveling at the same speed towards each other, does not "double the energy of the collision" in that way, as intuitive as it feels to think it would work like that. Two ideal cyclists (ie, of same mass) hitting each other head-on while traveling at 15mph each, will each experience a similar impact as if they'd each hit an ideal, solid cliff-face of stone, while traveling towards it at 15mph.
 

Timpo

Well-Known Member
Go back to school bud, you skipped the last few years of junior physics.
No, if you hit a stationary object at 15mph, the stationary object will be essentially pushing back just as Newton said, so it doesn't make any difference.
Hitting a stationary object & hitting something head on at the same speed will have the same energy impact.
 

Timpo

Well-Known Member
It will probably diverge the thread, but two objects of same mass, colliding with each other head-on while traveling at the same speed towards each other, does not "double the energy of the collision" in that way, as intuitive as it feels to think it would work like that. Two ideal cyclists (ie, of same mass) hitting each other head-on while traveling at 15mph each, will each experience a similar impact as if they'd each hit an ideal, solid cliff-face of stone, while traveling towards it at 15mph.
Exactly, the energy impact will be the same.

Here, I just did a quick YouTube research and looks like there are some video of it.

At approx 4:30, the video shows crashing at 50mph into a stationary object (in this case, they used a wall) vs crashing at 50mph head on at same speed (50mph) makes no difference, just as Newton's law of physics.

 

dAz63

New Member
It will probably diverge the thread, but two objects of same mass, colliding with each other head-on while traveling at the same speed towards each other, does not "double the energy of the collision" in that way, as intuitive as it feels to think it would work like that. Two ideal cyclists (ie, of same mass) hitting each other head-on while traveling at 15mph each, will each experience a similar impact as if they'd each hit an ideal, solid cliff-face of stone, while traveling towards it at 15mph.
MythBusters episode where they ran two cars into a wall, one at 50mph and the other 100mph, then they ran two cars head on at 50mph and the damage was equal to the car that hit the wall @ 50mph.
 

Deafcat

Active Member
Try it with bicycles some time, not an arbitrary test with advanced vehicles engineered around crash protection. While it may be true that two opposing moments may result in effects similar to hitting a stationary and fixed obstacle, it is NOT the same as say, hitting another stationary cyclist. the damage is much worse when they are both colliding head on at matching speeds, compared to one moving cyclist colliding with a stationary cyclist.
 

Timpo

Well-Known Member
Try it with bicycles some time, not an arbitrary test with advanced vehicles engineered around crash protection. While it may be true that two opposing moments may result in effects similar to hitting a stationary and fixed obstacle, it is NOT the same as say, hitting another stationary cyclist. the damage is much worse when they are both colliding head on at matching speeds, compared to one moving cyclist colliding with a stationary cyclist.
We're not talking about hitting a stationary cyclist. We're talking about head on collision.

Yeah, if you hit a stationary cyclist, pedestrian, joggers, etc.. you will be better off than hitting a stationary object or a wall since the person will be pushed over which effectively ease up your impact because they will fall over to the way you were travelling. (which works like a cushion)

However, we're talking about head collision when somebody else come towards you at the same velocity.
The argument here was a 15mph + 15mph = equivalent of hitting a wall at 30mph. Which is not true.
 

6zfshdb

Well-Known Member
Not good news for the cycling community. My prayers go out to the riders involved.

The thing that upsets me the most about the article is the comment about cycling groups protesting enforcement of the speed limit?? These folks are breaking the law and have the gall to protest when they get caught??
 

Deafcat

Active Member
However, we're talking about head collision when somebody else come towards you at the same velocity.
The argument here was a 15mph + 15mph = equivalent of hitting a wall at 30mph. Which is not true.
What I'm saying is that from a physics perspective, the collision energy of two head on cyclists is similar to a moving cyclist of the combined velocity hitting a stationary cyclist in the same orientation. You're correct that it's not the same as hitting a fixed wall at that speed, though.

You may certainly disregard my original comment about high school physics though! Cheers