Speeding would seem like the most obvious safety compromise. Speeding would seem like the most natural remedy to a schedule too tight, and the most obvious way to pick up more passengers, increase system capacity and maximize revenue: Just drive faster.
In truth, speeding is not the most significant safety compromise, and doesn't provide the time-or cost-saving benefits of many others in some public transportation sectors. But it can still be significant, and is often combined with other compromises -- increasing risk in the process. Otherwise, when employed often and/or excessively, speeding can compromise passenger safety, and that of fellow motorists, pedestrians and others outside the bus, significantly.
While excessive acceleration, deceleration and braking obviously involve changes in speed, the aspects of speeding covered in this installment focus mostly on plain-old speeding: Traveling beyond a reasonable, safe speed once the vehicle has reached it.
Mode by Mode
Both the tendency to speed and the opportunities to do so (and not get caught and cited for it) are different from mode to mode.
Fixed Route Transit Service. Opportunities to speed are often rare in fixed route transit service in urban and suburban areas, where the frequency of stops and medium-to-heavy traffic greatly constrains them. And even most commuter/express service speeds are constrained because of the traffic volumes of the peak periods during which they travel. The two major exceptions occur on sections of outer, suburban portions of routes operating on arterial streets, and for all transit buses, on arterial or collector streets where the distance between stops is significant and traffic volumes are moderate to low. These latter opportunities occur mostly during the "base" period and, more so, during the night and owl periods. But speeding is unmistakably tied to the realism of a bus' schedule.
Apart from the obvious increased collision potential of speeding (more serious with vehicles of large mass with understandably longer reaction time (from pneumatic brake systems) and much longer stopping distances (from their greater masses), speeding poses risks to passengers -- particular standees when buses must brake quickly from high speeds or take turns too fast. Rolling turns, for example, may occur within acceptable speed limits. But these speeds are often several times greater than a proper, "square" turn would produce. Nailing pedestrians traversing intersection crosswalks is a common consequence (see turningaccidents.com and crossingaccidents.com).
Motorcoaches (tour, charter and intercity/scheduled) Service. Much of motorcoach travel occurs on freeways -- where most of motorcoach speeding occurs. This practice is problematic for a number of reasons. First, traveling at ultra-high speeds in a vehicle of huge mass with pneumatic brake systems, the stopping distance for a motorcoach can easily be 600 to 700 feet -- far greater than that of a small automobile traveling in front of it. For these reasons, rear-ending a much smaller vehicle can easily occur, and will almost always cause catastrophic damage to it.
These dangers are far greater at night: Not only because of reduced visibility, but also because of the greater driver fatigue that stems from scheduling and driver assignment that ignores drivers' sleep/wakefulness cycles. Bio-sensitive driver assignment (see National Bus Trader, April and May, 2014) would greatly reduce this problem. But almost no motorcoach operator in any sector employs this. And the minimal use of screening for Obstructive Sleep Apnea (much less the limits of merely screening for it) further compounds the problem. Most catastrophic motorcoach collisions where drivers have fallen asleep at the wheel have also occurred at excessive speeds, especially those having occurred during the night and owl periods.
Where traffic constrains speeds, motorcoaches (along with other modes) commonly follow vehicles in front of them too closely. Tailgating in vehicles of such mass has the consequences one would expect.
Finally, the faster a vehicle is traveling, the more difficult it is to apply defensive driving techniques. Fellow vehicles, fixed objects and escape routes ("Leave Yourself and Out") just fly by, and at high speeds, defensive driving techniques are harder to executive. The risks are even greater when these techniques are not applied.
School Bus Service. Speeding is far less common in pupil transportation. In most places, routes are relatively short, stops are close together, passengers are young, and driver operating responsibilities (e.g., for directing the crossing of students in front of the bus) are varied and of intense importance. Some school bus schedules are indeed too tight -- but not as common as in transit (where in some large urban systems, every route's schedule is tight). But students are not allowed to ride as standees, and in fact, and not supposed to even arise from their seats until the bus comes to a complete stop. And similarly their buses are not allowed to pull out until all passengers are seated. The presence of bus monitors on board many school buses also helps to maintain passenger control. Finally, far less school bus service operates on high-speed roadways. When it does, there is usually less pressure to exceed appropriate speeds. Finally, the important goal of never arriving early to a pickup or drop-off limits the incentive to speed.
Paratransit Service. Whether ADA-required service for transit agencies or other purposes, most paratransit vehicles do not speed -- even while the predominance of software commonly creates schedules too tight. Paratransit services commit many other safety compromises (e.g., wheelchair and passenger securement failures), where the commission of a single safety compromise can shave several minutes off a route's running time. But largely because of the local and sub-regional nature of most paratransit trips, the vulnerabilities of the passengers, and the great amount of digital equipment available to monitor service (mobile data terminals, automatic vehicle locators and other GPS-related devices interfaced with their often high-digital operations), speeding is not a major problem in most paratransit services.
Non-Emergency Medical Transportation (NEMT) Service. Because most NEMT service is paid for via taxi-type rates ($X/trip plus $Y/mile), almost every safety compromise available, including and beyond speeding, is employed in the provision of NEMT service. This is because NEMT services earn no money unless the vehicle is moving, and obviously things must be done when it is not (loading, unloading, wheelchair and passenger securement, stopping at traffic signals and stop signs, etc.). So speeding is rampant in this sector, and combined with other errors and omissions (e.g., failing to secure wheelchairs and their occupants into them), speeding combined with inertial and centrifugal forces lead to a considerable number of wheelchair tipovers, and other incident scenarios. Low-paid service providers, low-paid drivers, driver shortages and the almost total absence of spare vehicles and drivers compound these problems. These consequences are often not solely the drivers' fault, but instead, the consequence of the mode's poorly-conceived and minimally-controlled operating environment, and the complete lack of monitoring. But traveling "too fast for conditions" (a legal cliché) is a major contributor to the large number of incidents in this sector.
Taxicab Service. Taxis are known for speeding. Like NEMT service, this is largely the result of the mode's rate structure: $X/trip (known as the "flag drop" in taxi lingo) plus $Y/mile combine with the low wages taxi drivers typically earn to induce them to often ignore speed limits and, to some degree, drive as fast as they can. Often the trips are long. And as an exclusive ride mode, there are no intermediate stops between the single origin and destination to periodically slow the vehicles down. The dynamics are further compounded by the fact that at least half of a driver's "take" from the fare covers the cost of the vehicle and services typically associated with it (e.g., dispatching, and in some cases, maintenance). As a result, a typical full-time taxi driver operates a 72-hour week -- where fatigue compounds the risks of speeding. Finally, as taxi densities have been thinned in recent years by the incursion of transportation network companies (TNCs) like Uber and Lyft, deadhead time has increased. So when fare-generating passengers are onboard, service is even more frantic than it was when taxi services at least owned their market.
Reality and Consequences
While speeding can be dangerous in general, its biggest problem involves speeding around turns. This is because centrifugal forces become exaggerated. The faster the speed around the arc of a given turn, the greater these forces will be. In worst-case scenarios, speeding around tight corners can result in a rollover. Far more commonly, passengers are thrown out of their seats. Even more common, and usually resulting in much greater injuries, are wheelchair tipovers. (See wheelchairtipovers.com.)
Also, posted speed limits are not always realistic. This is because law enforcement and traffic engineering officials realize than many common motorists will exceed them. So they are often posted lower than necessary, other than in politically-sensitive areas (e.g., suburban areas where children are more likely to cross streets or play in them). Because of more common and less predictable occurrences in rural areas (e.g., deer running into the roadway) and the exaggerated curvatures of streets in rural areas compared to those in most urban and suburban areas, speed limits in rural areas are often more accurate, and more important for motorist to obey. But for buses and motorcoaches, with pneumatic brake systems and greater masses, speeding translates into longer reaction time distances and exponentially longer braking distances. So compliance with speed limits while operating large vehicles is a necessity.
As a concluding point, speeding is a far greater problem in public transportation than in personal transportation. Either the passengers are more vulnerable, the vehicles are heavier (and have longer reaction time and larger stopping distances), schedules are too tight (inducing the commission of safety compromises) and/or naive and dysfunctional rate structures encourage speeding. Factors beyond the control of the transportation industry -- like changes in the distribution of wealth that have lowered drivers' salaries in real-dollar terms over the past few decades, and the intrusion of new modes into the service areas of traditional modes -- have made speeding even more attractive and more problematic. As a policy-making and management matter, transportation officials should be aware of these dynamics and do what they can to minimize this safety compromise, and the carnage and litigation consequences that so often accompany it.