Why did SEPTA bother with push-pulls?

[train2]

Yesterday I was riding home on the Paoli line on an express made up of Silverliners and this thought crossed my mind: Why did SEPTA bother with push-pull trains? What did they do for SEPTA that the MU car fleet did not provide? Given that 90 plus percent of the rail operations are MU cars, I see the sue of push pulls as counterproductive. SEPTA has to have another line of parts for cars and engines, they have to train and test crews on different equipment, different inspections, etc, etc.

Did the Push pulls go faster, seat more (or the opposite, seat less more conformably).

My express of MU cars seemed to do the trick. And I was wondering what the other train sets do that my MU car did not do?

Only now with the future introduction of double decker locomotive hauled cars do I see an advantage. But that is in the future and 30 years after they started the practice.

[mcgrath618]

Push pulls are not only cleared for (and able to do) faster speeds, but are also far more comfortable. It’s also very inefficient to string together 6-7 SLIVs or Vs, whereas having push-pulls is far more efficient.

[NorthPennLimited]

Here are a few pros / cons. I’m sure the experts can add to the list.
PROS
*You can haul more cars (people) with one crew. Train sizes are limited to 6 MU cars on the Reading side due to substation load capacity. Less crews carrying more people = lower operating labor costs.
*Coaches don’t need FRA 90 and 180 day inspections which reduce shop manpower needs and equipment dwell time in the shop
*Coaches are less expensive to purchase. No propulsion systems, control stands, PTC, etc.
*Less parts = less items to find failure during calendar day inspections and brake tests
*When a coach fails, you loose 1 car. When a MU fails, normally, you loose a married pair.
*Coaches are interchangeable with other railroads and locomotives. This diversity increases their chances of finding a buyer in the used market if they need to be sold or leased.
*Locomotives have greater mass, making them safer in a crash at a road crossing collision.

CONS:
*Push-pulls can’t rival the acceleration rates of an MU, thus increasing trip times on local trains due to start/stop.
*The locomotive is the only source of propulsion, HEP, and air for the brakes, thus a single point of failure in a breakdown / train cancellation.
*They are over-kill during non-peak travel times and waste electricity if used outside of rush hour.
*They take up more mid-day storage space between AM and PM rush hour.
*They require another supply of parts to keep in stock at repair shop yards
*They can’t serve small branch lines with small station platforms efficiently without causing excessive station dwell time

[CNJGeep]

In 1986, SEPTA was ready to purchase a fleet of Silverliner V MUs. At that time, Amtrak was sounding alarm bells that they were going to divest themselves of the Keystone Corridor if the state didn't step up funding big time. There was serious talk about SEPTA picking up this service. HOWEVER, the collision at Chase, MD forced SEPTA's hand since they needed an immediate replacement for the Reading Blue MUs and the PRR Pioneer III cars (245-250), as they would no longer comply with changes to federal regulations. These two circumstances combined to result in a push pull order.

SEPTA was getting ready to jettison the push pull fleet in 2008, but the huge ridership spike brought on by $4/gallon gasoline put an end to that plan.

Of course if you ask a naysayer they'll say there was a backdoor deal....read into that how you will.

[MACTRAXX]

T2 and Everyone:

Almost ten years ago we had a discussion about this subject titled "Purpose of Push-Pulls".
viewtopic.php?f=72&t=54731
This older topic can add insight to the current push-pull train questions...

I agree with what CNJ says about how SEPTA acquired their push-pull fleet and will add that time
was of the essence then to retire the RDG Blueliners and the five 1958 vintage Budd Pioneer One
MU cars (correct numbers: 244 to 248) back in 1987 and this was the quickest fleet addition that
was possible over going through a design process and long lead time for new MU cars.

When the AEM7s and Bombardier cars were new SEPTA tested them on multiple routes including
routes such as the Chestnut Hill East and West lines with multiple stations that are close to one
another. From those tests this new fleet was best operated on longer lines with more distance
between stations. These test runs were on assigned peak hour trains for a weekly period - and
one I remember riding - a CHE run - the AEM7 was barely able to get going before braking for
the next station. For short runs or lines with many station stops MU cars were - and are - best.

From reading the 745 page guide about the new multilevel cars I noticed that this new fleet will
be primarily slated for three lines: Paoli-Thorndale, Wilmington-Newark and West Trenton.

It will be interesting to see how SEPTA places the new ACS64 Sprinters in service and retire
the now 30 year old AEM7s and the one remaining ALP44 over the next two or so years...

MACTRAXX

[train2]

What is the difference in max speed for the push pull sets vs the Silverliners?

[mcgrath618]

What is the difference in max speed for the push pull sets vs the Silverliners?

SLIVs can do about 70 max, but usually stick to around 60, whereas the SLVs can handle about 90, and usually do AT THE MOST 70. The AEM’s can do about 110 if you try really hard but stick to about 85 at the max.
This is based off of my experience on the R5. Take this with a grain of salt.

[R3 Passenger]

I've clocked a set of Silverliner IVs at around 90 mph and a set of Silverliner Vs around 94 mph on an express run up the NEC to Torresdale.

While the AEM-7s are designed for 110 operation, they never get that high since the coaches are only cleared for 100 in pull mode and 90 in push mode (from what I understand).

[CNJGeep]

Silverliner IV: 90
Silverliner V: 100
AEM-7/ALP-44: 100
Bombardier Coaches: 100
ACS-64: 110

[silverliner266]

Silverliner IV: 90
Silverliner V: 100
AEM-7/ALP-44: 100
Bombardier Coaches: 100
ACS-64: 110

Worth noting that SEPTA's AEM-7s and Sprinters have lower top speeds than Amtrak's and I believe it's because they are geared for better acceleration rather than top speed.