The opinion
ROBB, Circuit Judge,
concurring in part and dissenting in part:
I concur in Part III of the court’s opinion, upholding the EPA’s grant of NOx waivers to various diesel manufacturers. I must dissent, however, from that part of the opinion in which the court sustains the particulate standards for 1985. In my view the record does not support the EPA’s prediction that the necessary technology will be available in time to meet the 1985 standard. My doubts focus in particular on the inability of the auto manufacturers to develop a filtering material for trap-oxidizers that possesses the durability needed to withstand periodic incineration of collected particulates for the useful life of the vehicle.
The majority states that “the EPA will have demonstrated the reasonableness of its basis for prediction if it answers any theoretical objections to the trap-oxidizer method, identifies the major steps necessary in refinement of the device, and offers plausible reasons for believing that each of those steps can be completed in the time available.” Ante at 331. I have no quarrel with this standard, but I do not agree that the EPA has offered plausible reasons for believing that the critical step of achieving the required level of trap durability can be completed in the time available.
The record demonstrates that General Motors (GM) alone, which began its particulate control research program in 1974, has tested many different trap materials provided by at least 16 different manufacturers. 1 Of these materials, 22 are characterized by GM as “the best materials” available, 2 based on tests conducted with an Opel 2.1 liter diesel engine and an Oldsmobile 5.7 liter diesel engine. (J.A. 237) Yet the durability of even the best of these materials— the metal mesh — is far below what will be needed to meet the standard. The most successful test results were obtained by installing a metal mesh trap in a GM Opel, which was then driven on a non-typical schedule with no hard accelerations, hills, or speeds above 45 miles per hour. The filtering material survived only 12,800 miles, at which time it had a collection efficiency of 55 percent. GM also reported some particulate “blow-off” (i. e., particulate matter escaping through the exhaust system) and self-incineration. (J.A. 530) The statute, however, establishes a useful life for light duty vehicles and light duty vehicle engines of “five years or fifty thousand miles (or the equivalent), whichever first occurs.” 42 U.S.C. § 7521 (d)(1) (Supp. I 1977). Furthermore, the EPA stated in its Regulatory Analysis of the particulate standards that the trapping material “should last at least 100,000 miles.” (J.A. 530)
After acknowledging the shortcomings of the Opel test, the EPA summarized the status of trap-oxidizer research as follows:
Clearly, more basic research still needs to be done in the areas of regeneration initiation and control, and trap durability. Enough progress has been achieved to convince EPA that a successful trap-oxidizer can be developed, but as of this time, no design has proven to have the required collection efficiency over the desired length of time. With the research that has been, and is, going on with regards to trap-oxidizer development, and a determined broad-based effort by the manufacturers to comply with the final standards, EPA’s technical staff has concluded that it is very likely that a successful trap-oxidizer design can be optimized within the next IV2 to 2 years.
(J.A. 531) In my opinion, these exhortations to the manufacturers and the EPA’s vaguely articulated faith that a “design can be optimized” soon do not amount to “plau *233 sible reasons for believing that each of [the necessary] steps can be completed in the time available,” within the meaning of the majority’s standard. Pious hope and speculation cannot take the place of evidence. Accordingly, I must dissent from Part II of the court’s opinion.
. Corrugated foil fecralloy; chopped fecralloy; chromium alloy ribbon; glass fiber fabric; fiberfrax fiber fabric; alumina fiber material; catalyst beads of a variety of types including quadralobe, trilobe, low density spheres, large quadralobe, porous ceramic, small bead, and “prod.” catalyst; ceramic monolith, extruded and low density; torturous path, ceramic; ceramic bobbin; metal mesh; alumina coated metal mesh; metal wool; paper; and fiberglass. (J.A. 238 — 42)