The underpass along Quezon Avenue (Radial Road 7 or R-7) for its intersection with Araneta Avenue (Circumferential Road 3 or C-3) is currently being constructed. The project was approved last year and it designed to relieve congestion at this busy junction of two major thoroughfares. Among the alternatives considered for the intersection was a 4-lane overpass to be constructed along Quezon Avenue similar in design to the overpasses in Iloilo and Cebu cities. One concern, however, that needed to be explained thoroughly by the DPWH to stakeholders, especially the Quezon City government, was the prospect of flooding. The area, particularly the part of Talayan Village, is prone to flooding with water reaching waste-level that can be brought about by heavy rains. It may even be worse for rainfall of the Ondoy or Sendong kind.
The project seems to be proceeding at a good pace with a lot of activities in the past months. Congestion does not seem to be as serious as what had been anticipated, thanks in part to an aggressive campaign that included information on alternative routes for motorists. Still, it is recommended for the motorist to avoid the area and use other routes if possible as traffic can test one’s patience in this area.
Some of the photos were quite dark as it was already past 5pm when I took them with a cell phone camera. I tried to adjust the brightness in order to have clearer images.
Manila-bound approach to the Quezon Ave.-Araneta Ave. intersection where there are effectively 2 lanes available to traffic. It can be quite congested here during the regular weekdays as the original 5-lane section Quezon Ave. narrowed to 2 lanes due to the ongoing construction of the underpass. There used to be a pedestrian overpass at the intersection. This had to be dismantled to give way to the construction of the underpass. Remnants of the overpass remain in the area.
At the intersection, the remains of what was a pedestrian overpass can be still be seen. The overpass crossed both Quezon Ave. and Araneta Ave., allowing for pedestrians to walk across the intersection without conflict with motor vehicles below.
The intersection itself has not been excavated and it will be a “Herculean” task to manage traffic once this phase of the project is implemented. Both R-7 and C-3 are high volume roads and the MMDA and QC enforcers would have their hands full, and definitely more challenging than what they are contending with at present. This intersection will still be at-grade in the future and should feature a traffic signal to manage the remaining traffic movements as through traffic along Quezon Ave. will eventually flow continuously along the underpass.
A good thing for the project is the approaching school break after March 2012. Should construction proceed at the current pace (or even faster) they should be able to have the underpass operational by the time school opens in June 2012. The contractor should take advantage of the typically good weather in Metro Manila from January to May so as to finally relieve road users of the inconvenience caused by the project implementation. On another note, the underpass is similar to what was proposed for the case of C5-Kalayaan before the MMDA decided to turn that intersection into a showcase for their U-turn scheme, culminating in the construction of 2 U-turn overpasses in the area. The completion of the Quezon Ave.-Araneta Ave. underpass coupled with an effective traffic signal system setting at-grade may just prove the DPWH right in their pitch for the same intervention at C5-Kalayaan and revive discussions pertaining to a more effective solution to the congestion there.
I saw the tarp below posted along Katipunan Avenue as we drove to UP one Saturday morning. There are actually two signs: one in front of Ateneo Gate 1 and the one below just after Ateneo Gate 2. Both speak out to the Quezon City Council for issuing an exemption to SM Development Corporation (SMDC), part of the SM group of shopping mall fame, for its high-rise condominium development near the corner of Aurora Boulevard and Katipunan Avenue (C5). The development, known as Blue Residences, will not only have residential units but commercial establishments as well. By the name of the project, it is obviously a play on the nearby Ateneo De Manila University, which has blue for its standard color (e.g., Blue Eagles). [Note: For whatever its worth, there is also a Green Residences being developed by SMDC near De La Salle University, which adopts green as its banner color – e.g., Green Archers.]
The questions going in my mind after seeing the signs include the following:
1) Isn’t it too late for this, a campaign against a development that is already under construction and months after a decision has been made to approve the project?
2) What is Ateneo’s and its allies success rate for such? [The high density developments just across the university seem to be concrete evidence and reminders of such actions falling on deaf ears.]
3) Given this seemingly renewed (not new-found, I hope) interest in urban development in the area, wouldn’t it make more sense to also campaign against another development, this time by another real estate giant in Camella/Vista Land that already has set up shop across Ateneo?
4) And, as a follow-up perhaps, has that strip along Katipunan already been ceded to high density development and Ateneo and its allies have already conceded that a long time ago? [There’s SMDC’s Berkeley Residences, Prince David, Burgundy, etc.]
A colleague put forward an opinion that such developments are actually beneficial to Ateneo and its allies. In fact, many of the residents of the high rise condominiums in Katipunan have children studying at Ateneo and Miriam, their addresses being conveniently located minutes away from school. In other cases, units are rented by university students who similarly take advantage of the building’s proximity to their schools. I wouldn’t be surprised if enterprising people have purchased units not for them to reside in but to rent/lease out to students or other wishing to live near the universities or the nearby LRT 2 station (Katipunan Station).
From the traffic perspective, such developments definitely require full-blown transport or traffic impact studies due primarily to their trip generation characteristics. Such studies should clearly show how to address potential transport and traffic problems including who will be responsible (hint: the proponent should not pass on responsibility to the MMDA or local traffic enforcement) for traffic management. I reproduce below excerpts from a report submitted by a stakeholder community in opposition to a proposed high-rise, high density mixed-use (commercial, office, hotel and residential) development at the corner of EDSA and Ortigas Ave. where a huge excavation is still present and can be clearly seen when riding a Makati-bound MRT train:
“The EIS Report failed to consider the traffic impact once the project starts to operate hence necessary measures were likewise not discussed. Many projects will, at first glance, give an impression that a traffic impact study would not be required. The Skycity development, however, immediately gives the layman an impression that it would indeed have a significant and long-term impact on traffic in its direct vicinity. While its influence area can only be clarified via a thorough study of the characteristics of the development, the description and hype alone by the project proponents give us an idea that Skycity will impact people from as far as Rizal province.
In the process of attaining these objectives, this paper will identify the deficiencies and weaknesses pertaining to transportation and traffic and establish the need for detailed traffic studies, specifically the requirement of a Traffic Impact Study (TIS). The TIS will entail traffic impact analysis (TIA) to satisfy the questions or concerns regarding the traffic generated/attracted by the Skycity project and the consequent problems that will be caused by the project from its construction to eventual operation.
A traffic impact assessment (TIA) would be imperative, if truly the effects of the development would be quantified. The TIA would be able to answer the following questions, among others that would crop up in the minds of stakeholders:
- What are the transportation improvements needed to serve the traffic generated by the new development?
- How much will the improvement cost be and who will pay for them?
- Will the new project impact traffic on any existing residential streets and how will those impacts be mitigated?
- Will the new development aggravate any existing safety hazards or create new ones and, if so, how can those hazards be corrected?
- Can the proposed development be served by public transportation and does the design encourage ridesharing?
- Is the design of the development friendly towards bicyclists and pedestrians who need to access the development or who need to pass through or by the development?
- Is the on-site parking sufficient or is there an opportunity to share parking with other adjacent uses?
- How many driveways are needed, what design should each driveway have and is there a long enough throat for each driveway that is clear of parking spaces and other cross aisle traffic?
- If any driveway is proposed to be signalized, is the traffic signal really needed and can on-site circulation handle the traffic that will be queuing to wait for a green light? (
Conduct of TIA will deal with deficiencies in traffic analysis as well as provide a platform for a package of measures to deal with issues: what measures? who will pay? what level of development? Until then, it’s not possible to concretely evaluate the EIS.
Concerning traffic, the GEA letter raised the following points:
- That traffic congestion at EDSA-Ortigas intersection is already a nightmare even without the Skycity on that particular corner;
- That the traffic congestion problem can be attested by key agencies such as the Mandaluyong City Mayor’s Office, the MMDA Traffic Management Group, the Barangay 27 Wack Wack Greenhills East and the nearby DOTC, all of which are helpless in providing solution to the problem;
- That the already grave traffic congestion will even worsen due to obstructions and additional traffic during construction and operation of Skycity;
- That Ortigas Avenue is too narrow to accommodate the high volume of traffic; and
- That provision of several parking floors as presented in the EIS cannot be a solution.
“Manpower requirement will be high during the operations phase. It is estimated that about 12,000 persons will be required to for the operations and maintenance of the Skycity Project. These would include the general administration, manpower for the utilities and security, and employees for the hotel. Man power for the commercial, office establishments and other development use of the project will add a few thousand more jobs.”
The above quotation is from a report submitted as part of the response of stakeholders that scrutinized the Environmental Impact Assessment (EIA) report submitted by the proponents of the project to the DENR-EMB. The latter was presented at a stakeholder conference held as a prerequisite to the approval of the project (i.e., prior to granting an ECC). There are other aspects of the project including drainage, water supply, structure, foundation, environmental, etc. that were discussed with proponents and stakeholders arguing about the pros and cons of the project. However, the most important element here is timing since the discussions occurred prior to the granting of an ECC to the project and after the stakeholders have presented their case before the DENR-EMB’s EIA Review Committee assigned to the project. I am not aware of how SM Blue went about securing the approval for their project including the ECC and if the process was followed according to the guidelines. I am also not aware of whether there was a stakeholder conference held and if Ateneo and its allies were invited and participated in that meeting. Was this organized by the EIA RevCom or was this hosted by the QC Council (because of the zoning issue)? Such matters are important since it would help in establishing whether certain people are at fault and whether certain processes and requirements were indeed followed with regards to the project being questioned.
Driving to my in-laws’ home the weekend before Christmas, I was able to pass along the newly paved section of Commonwealth that now connects directly with Quirino Highway. While there are still much evidence of the construction project like materials and soil from excavations, traffic signs have been installed and pavement and curb markings were mostly completed including the yellow box.
One can compare the photos below with those in an earlier post found here.
The intersection at the Jordan Plains gate already has directional signs showing the way to points of interest like the Novaliches District Center (sort of a mini City Hall), General Luis road (via Jordan Plains Subdivision) and Quirino Highway, which is up ahead from the intersection.
On the day before Christmas, most leftover construction material were already removed from the area and the approach to the intersection is shown below. The 4-lane northbound side of Commonwealth becomes 3 lanes from the intersection. The opposite southbound direction with 3 lanes widens to 4 lanes after the intersection.
So far, I have only observed light traffic along the intersection but this should eventually become a major intersection and may require traffic signals once motorists become more familiar with this route. Already there are some experiences of congestion at the intersection with Quirino Highway as it is currently unsignalized despite the volume of traffic at the area. Considering the typical behavior of motorists, it is not unthinkable that conflicting flows eventually translate into constrictions as drivers generally do not give way even to those with a clear right of way. Thus, manual enforcement will have to be present, firm and consistent in order to be effective in managing traffic at Commonwealth-Quirino.
To continue with our feature of Philippine airports, I am posting photos on the airport in Cagayan De Oro City collected over the past few years. The airport is curiously located on a plateau making it difficult to expand the airport, particularly lengthen the runway to accommodate larger aircraft. The airport is also plagued by poor visibility due to its elevation, which makes it prone to fog during the wet season. I am a frequent user of the airport due to trips to Iligan City where we have research and extension involvement with MSU-IIT and the City Government of Iligan, mostly to promote environmentally sustainable transport. MSU-IIT and UP Diliman are also among the partners in the DOST’s Engineering Research and Development for Technology (ERDT) program together with Ateneo De Manila University, DLSU, UPLB, Mapua, CLSU and Cebu’s University of San Carlos.
Following are photos from a trip to Iligan City back in September 2007. The gateway to Northern Mindanao, we usually travel to Iligan City via Cagayan De Oro.
I was able to take photos on a September 2009 trip to Iligan City. This was only a couple of weeks before Ondoy (Ketsana) inundated Metro Manila and much of its surrounding areas.
Passengers deplaning from the aircraft’s rear (aft) door. That’s Prof. Tetsuo Yai of Tokyo Tech smiling as he descends from the plane. PAL’s staircases actually look more sturdy than the makeshift ones used by CebPac.
Ceb Pac turbo prop aircraft (ATR 72-500) loading passengers. These aircraft typically serve shorter routes like CDO-CEB or CDO-DVO. Jet aircraft (A319, A320 or A330) usually services the longer domestic routes like CDO-MNL or DVO-MNL.
The following photos are from a more recent trip to Iligan (July 2010) via CDO. At the time, we held a seminar/workshop at MSU-IIT on EST that focused on the application of a road accident database system developed by NCTS for the DOTC.
After deplaning, passengers walk towards the terminal. People are supposed to be prohibited from walking along the area under the aircraft’s wings so security typically lay down traffic cones for this purpose.
From 2012, or perhaps 2013 if delayed, the main airport for Northern Mindanao will be transferred to Laguindingan town, a few minutes away from CDO. The region, after all, deserves a bigger and better airport. The land where current airport is located will most probably be sold or leased out, similar to what was done to Iloilo’s airport in the Mandurriao district of that city. I am quite curious if the Laguindingan airport construction was affected by the recent floods brought about by Sendong (Washi). That storm laid waste to large areas of Northern Mindanao and particularly costing the lives of more than 1,000 people based on the latest reckoning. It is hoped that Northern Mindanao and other areas affected by the recent calamity would be able to recover and quickly. The people are resilient and hopeful, and should be aided for them to be able to rise from this terrible experience, a tragedy of the highest magnitude.
Graduate students majoring in Transportation Engineering at the University of the Philippines Institute of Civil Engineering (UP-ICE)currently conducting their research through the NCTS presented during the graduate seminar held last December 15, 2011. There were 4 presentations made during the seminar, which was attended by 3 faculty members of the UP-ICE: Dr. Karl Vergel, Dr. Sean Palmiano and Dr. Regin Regidor. Following are a few snapshots from the seminar, which was facilitated by Mr. Ernesto Abaya, D3 student under Dr. Vergel, who is also a technical staff of the NCTS.
Mr. Nirman Pokharel, a Nepalese student presented on the progress of his research on the public utility jeepney (PUJ) application of Auto LPG. Mr. Nirman is also working with researchers of the Vehicle Research Testing Laboratory (VRTL) of UP Mechanical Engineering.
Ms. Anna Tiamzon presented her preliminary research proposal on walkability. She is a faculty member of the University of Sto. Tomas (UST) in Manila.
Mr. Edmon Favila presented his preliminary proposal on fare setting for UV Express services (van-type service) in Metro Manila.
Mr. Ali, an Iranian student, also presented a preliminary topic on the determination of bus terminal locations for Metro Manila.
Other graduate students who were not able to present in the December seminar will be making their presentations in January 2012 including two PhD program students and 3 MSCE students. The undergraduate students of the Transportation Engineering Group (TEG) of UP-ICE made progress presentations earlier last December 7, 2011 and are on-track to complete their researches by March 2012.
I was able to take some photos along Marcos Highway before the rains came over the weekend just to have a handle on the current state of roadworks along that road. I had written recently about the progress along Commonwealth Ave., particularly the stretch connecting to Quirino Highway. In that project, the contractors constructed a culvert across Commonwealth that took quite some time and yet has been completed many weeks ago.
Unfortunately, for those using Marcos Highway, it seems the inconvenience (to use a diplomatic word) will continue on considering the seemingly chaotic approach the contractors have been employing in digging up the pavement. Of course, it is a major project and I am sure many people will ultimately be thankful for the new drainage (hopefully, it’s maintained well) and the brand new pavement that will make travel smoother. But then the completion of the Marcos Highway works seem quite far in the horizon and has effected tremendous losses in travel time and fuel.
Section across Burger King and in the vicinity of a U-turn slot intended for traffic generally coming from Imelda/Felix Ave. The site is a bottleneck for traffic coming from Masinag and the villages along Marcos Highway. Due to the road works and the U-turn slot, there are only 2 lanes effectively available for through traffic that originally flowed along 4 lanes.
Past the bottleneck, the Marcos Highway seems quite spacious with the equivalent of 3 lanes suddenly available to motorists. At right, there is the work area of a water concession who is supposed to coordinate with the road project contractor.
Newly paved lane at the approach to the junction with Imelda Ave/A. Tuazon Ave. The works at this intersection has affected turning traffic to and from A. Tuazon Ave. At one time, right turns from Marcos Highway were prohibited due to construction affecting the entire intersection exit to A. Tuazon itself.
After passing Dela Paz and approaching Ligaya, motorists will usually encounter another bottleneck due to the U-turn slot for vehicles generally coming from Amang Rodriguez (Pasig) and bound for Marikina. The area is usually constricted even with traffic enforcers present. These enforcers are usually found engrossed in checking for number coding violators than managing traffic. At present, there project contractor has paved the innermost lane of the section and this morning that lane is already passable to vehicles. Problem is, the same vehicles will discover that they will eventually run into the U-turn slot and motorists would have to swerve right to converge with through traffic.
At the intersection of Marcos and Rodriguez, the traffic enforcers (probably in coordination with the contractor) made an opening to allow for counterflow during the peak periods. This is supposed to alleviate congestion at the intersection where aside from the still unfinished works, jeepneys tend to congregate and constrict the flow of traffic. Such occurs on a regular basis and one wonders how Pasig and MMDA enforcers can just stand around and not do anything about this predicament.
After Ligaya, traffic flow is split with vehicles maneuvering left and right to avoid road works along a middle lane of Marcos Highway. The pavement on the right most lanes are newly constructed and have been passable for some time now. From the looks of the pavement on the left, these two will soon be scheduled for re-blocking. Perhaps the lane under construction now will be finished by then.
There are also drainage and road works ongoing on the other side of the highway and right in front along the LRT2 station. Often, commuters can be seen taking one lane of Marcos Highway as they try to get their rides from jeepneys who occupy yet another lane or two. During the night-time, another counterflow scheme is used for eastbound traffic with an opening just after the bridge.
Of course there is hope for those using Marcos Highway regularly. Perhaps the project will be completed before school opens in June 2012 and by then flow will be smoother and congestion more bearable. We only need to look at Ortigas Ave and its extension to know that we are still quite lucky. It is far worse along that road.
San Francisco’s trolley buses are probably among the last of a fading breed of bus transport still employing electricity to service various routes in that city. With a cousin driving our vehicles along McAllister Street, I was able to take photos of the overhead cables from which the trolley buses are able to pick-up electricity to power their motors.
Where buses turn, cables may also be found above. This is the junction of McAllister and Van Ness Avenue. That’s the Herbst Theater building on the left, which houses the Museum of Performance and Design, and the California Public Utilities Commission on the right. Those are two buses, one trolley and the other natural gas-powered in the middle of the photo.
In the streets of San Francisco, one thing’s for sure – if you see those overhead cables along a road, you know that the trolley buses run along that street. Most major streets in San Francisco are served by public transport, providing excellent mobility for its citizens. They say you can usually take or get off a bus within a block of your destination. If you have to walk, the walk is usually at a leisurely pace and generally in a safe environment. You’ll probably only encounter difficulties walking when you’re in the hilly areas like Nob Hill and Russian Hill where the streets can get quite steep. Still, the walk’s usually well worth it not just because of the exercise but also because of the view and the small neighborhood shops and restaurants along your way.
Over the weekend, I happened to pass by what used to be the north end of Commonwealth Avenue near the back entrance to Jordan Plains Subdivision. Public utility jeepneys and private cars commonly use the subdivision streets to go to and from the Novaliches town center (Bayan). As such, the subdivision bears much of the negative externalities brought about by mostly unwanted through traffic. These include vehicle emissions and noise from motor vehicles, and the incidence of crime (mostly burglaries) in the subdivision. Too long have they waited for Commonwealth and Quirino Highway to be connected to reduce through traffic and its unwanted derivatives in the subdivision.
After delays due to various reasons, the project was finally bidded out and implemented this year. The construction didn’t go without any problems and there were times particularly during rainy days when the site was quite difficult to traverse due to excavations, materials and a so-so traffic management scheme (mostly counterflows) that ensure vehicles traveling as if they were negotiating a labyrinth. Still, work went on and at least people saw that it continued unlike other projects that went untouched after some excavations were made (“naka-tengga”).
I guess it was quite rewarding and a relief to a lot of people that the project will be completed soon and hopefully within the year and apparently on schedule. Following are a few photos of the area I took last Sunday.
First look at the approach to the completed section of Commonwealth Avenue connecting to Quirino Highway.
Closer to what used to be a chaotic intersection towards Jordan Plains, it was clear that most of the major works have been completed and that the section to Quirino was passable. The only elements missing are the pavement markings and traffic signs.
Kudos to the contractor of this project and the DPWH and Quezon City government for the near completion of the project. Now, if only the contractors of roadworks along Marcos Highway and Ortigas Avenue will follow the Commonwealth example and get their acts together and work more efficiently, not to mention do a better job managing traffic along the way, then probably people using those roads will have less headaches during this season.
San Francisco has an extensive public transport system with the combination of buses, LRT’s and cable cars allowing its citizens and visitors both accessibility and mobility for much of the city. A friend says that the objective Muni set out to accomplish was for anyone using the system to be able to alight from a public transport vehicle at most one block from one’s final destination. A block already represents a very comfortable walking distance well within the 200 to 300 meters radius often mentioned by public transport planners for the catchment areas of stops or stations.
SF’s Muni operates several types of buses including what are probably among the last electric trolley buses in the world.
That’s a trolley bus in the photo above stopping near the BART station where I was waiting to be picked up by a friend. Note the flexible, long pantograph that is used to pick-up electricity from the overhead cables. The photo was taken in 2007 during a previous trip to the Bay Area.
Following are three photos I took back in 2007 at an intersection across the Balboa Park BART Station, where I thought I hit the jackpot in terms of watching the Muni’s various transport modes pass by. Think bird-watching but replace the birds with buses and LRTs.
The typical Muni bus has a number designating its route that can easily be found in transit maps to guide regular commuters and visitors alike. Most buses I saw had bicycle racks located in front of the bus that would enable cyclists to bring along their bikes during a long commute. Most buses these days run on natural gas. On the far right of the photo, one can get a glimpse of a LRT vehicle.
LRT crossing the intersection. LRTs are given priority at intersections and the traffic signals are programmed to facilitate the flow of these high capacity public transport mode. This is a reflection of prioritization of public transport over private transport, which should be the case rather than the other way around.
Inside a bus in San Francisco, there are seats provided for the elderly and the physically challenged. Entrance is via the front door where a passenger must first pay for the ride or show his pass for the driver to see. Exit is via the back door, which is wider to allow for the efficient unloading of passengers. To stop the bus at the designated stops along the route, a passenger should push a button (on the newer buses) or pull on a cable (on older buses) to activate a signal for the driver. To open the rear doors, one need only to push the bars across the doors.
Another look at the interior of a Muni bus. Although the bus appears to be old, it is clean/tidy. There are the occasional vandalism and there are signs asking passengers to report incidence of vandalism on the bus. There are also signs stating that conversations may be recorded and that the bus is under video surveillance. These seem to be standard security features of public transport in the US especially after the incidents of 9/11. Such information is welcome considering everyone would prefer to travel safely.
I noticed a lot of interest on the “truck ban” scheme from the statistics provided by WordPress on my dashboard. It seems there are very limited material available on the scheme especially in the Philippines where there have been variations of and misconceptions on this travel demand management (TDM) measure. Why do cities like Metro Manila implement a truck ban? Or better yet, why are there designated truck routes in cities? The answer can be quite simple if viewed from the perspective of asset preservation. That is, by restricting trucks to use specific roads, we are also limiting their impacts (read: damage) to the road infrastructure. Such impacts come in the way of damaged pavements and/or bridges that bear the brunt of the weights carried by heavy vehicles. But such argument begs the question of why, in the first place, shouldn’t we design our pavements and bridges so that they may be able to withstand the cumulative loads of heavy vehicle traffic over a prescribed period of time, say 20 years, give and take a few years for variability and reliability in design and construction methods? Such is a question that needs to be answered, and clearly, by our DPWH, at least for the case of our national roads and bridges. It is really not a simple matter and certainly not something that cannot be blamed solely on the fact that evidences in the Philippines point to truck overloading as one of the culprits for damaged pavements and bridges.
The website of the Department of Public Works and Highways provides information on the axle load and truck weight limits for national roads. The matrix of weights may easily be downloaded and is provided in the following document:
The maximum single axle loads for different countries around the world are provided below:
I found another table of values this time for European countries. Based on the table on weight limits in European Union Countries, France seems to have the heaviest single axle load limit.
Still, the question running in the minds of most people involved in policymaking, monitoring and enforcement, and research is “How did we come up with the 13.5-metric ton maximum single axle load value in the first place?” Surely, it wasn’t a number that was plucked out from the air?
The 13.5-metric ton was most probably derived from an axle load study conducted in the 1990’s. Such a study could have, among others, determined the appropriate maximum axle loads that could be adopted by the country in lieu of the limits at the time that were already deemed obsolete given the evolution of trucks over time (i.e., they’re bigger now compared to, say, 30 years ago). What is problematic is that it seems the study was only able to derive the maximum single axle load and was not able to estimate maximum loads for tandem and tridem axles. Tandem axles are two axles positioned one after the other while tridems are three axles grouped together. These tandems and tridems are typical configurations for the rear axles of large trucks and trailers, enabling them to support heavy loads that typically are distributed more towards the rear axles.