“[W]hen an automobile is stopped in a public place with probable cause, no more exigent circumstances are required by art. 14 [of the Massachusetts Declaration of Rights] beyond the inherent mobility of an automobile itself to justify a warrantless search of the vehicle.” Commonwealth v. Motta, 424 Mass. 117, 124 (1997). In this case, we conclude that this principle applies even when the police had ample opportunity to obtain a search warrant, provided that there has been no unreasonable delay.
*555Facts and proceedings. The essential facts are not disputed. Members of the Berkshire County drug task force (task force) received information from a number of confidential informants that an individual named “Bill,” whose physical description matched that of the defendant, was selling “crack” cocaine from the parking lot of a tire store in North Adams. Confidential informants, who had purchased drugs from “Bill,” also reported that the individual regularly sold crack cocaine from a car wash across the.street from the tire store and sometimes drove to other locations to meet customers.
Based on the informants’ statements, in December of 2004, the task force undertook an investigation of the defendant, who worked at the tire store. The investigation established that the defendant routinely sold drugs from the tire store parking lot or the neighboring car wash before work, during his lunch hour, and at the end of the work day. Confidential informants told police that the defendant usually had crack cocaine when he was at work, either on his person, in his car, or both. Other informants1 provided specific details concerning two vehicles that the defendant used to conduct drug transactions. They also described the location in which the defendant hid cocaine and money in one of the vehicles. One informant, who had once observed the defendant with 112 grams of individually packaged crack cocaine, had purchased cocaine from the defendant on numerous occasions for several months prior to the investigation. Two informants stated that the defendant supplied named drug dealers with crack cocaine. One of these individuals, Joseph Pini, was known to the police as a drug dealer.
On January 5, 2005, an informant told members of the task force that the defendant was scheduled to receive a large shipment of crack cocaine sometime between 1 and 2 p.m. on January 6, 2005. On the same day, the investigators received information from an inmate at the Berkshire County house of correction that, *556on Friday, January 7, 2005, Pini intended to purchase a large quantity of crack cocaine from a dealer known as “Goodyear Bill,” who sold crack cocaine during lunch breaks and after work at the tire store. The inmate again contacted investigators on the afternoon of January 7, 2005, and reported that Pini told him that he intended to make the purchase after 5 p.m., when the defendant left work.
At 4:15 p.m., police began surveillance of the tire store, intending to follow the defendant after he left work and to arrest both the defendant and Pini after they completed the transaction. However, State Police Sergeant David B. Foley, a supervisor on the task force, observed that, because of the time of day, traffic on the streets near the store was very heavy.2 Foley became concerned that waiting to arrest the defendant and Pini, whom Foley described as a “nut,” until after they completed the transaction would create a risk that Pini, and possibly the defendant, would attempt to flee, and could result in a dangerous high-speed chase of one or both vehicles. He decided to forgo observing Pini and instead waited to observe whether the defendant left the store at the predicted time. He instructed the officers present to prevent the defendant from leaving the parking lot; he also decided that it would be wiser to arrest the defendant after the defendant entered the vehicle, rather than risk a struggle in the open lot.
At approximately 4:20 p.m., the officers saw Pini drive past the tire store parking lot without stopping. A few minutes before 5 p.m., the defendant left the store, started his vehicle’s engine, and then returned to the store. At 5 p.m., the defendant emerged from the store again. When he was seated in the driver’s seat of his white sport utility vehicle, police officers knocked on the driver’s side window and asked the defendant to turn off the engine. He refused to do so and attempted to put the vehicle in gear. After the police physically removed the defendant from the vehicle and took him into custody, they searched it. They found six plastic bags containing 379 grams of crack cocaine, two hydrocodone tablets, and over $2,000 in cash, including some counterfeit bills.
The defendant was indicted on charges of trafficking in cocaine, *557drug violations within a park zone, possession of hydrocodone, and possession of counterfeit bills. He moved to suppress all of the evidence seized from his vehicle, as well as statements he made at the police station after his arrest, on the ground that the warrantless search of the vehicle failed to satisfy any exception to the warrant requirement. This motion was denied. Following a jury-waived trial in the Superior Court, the defendant was convicted of the drug charges; the charge relative to the counterfeit bills was placed on file. The defendant then appealed from the judgments of conviction on the ground that his motion to suppress should have been allowed. The Appeals Court affirmed the convictions, Commonwealth v. Eggleston, 71 Mass. App. Ct. 363, 366-367 (2008), and we allowed the defendant’s application for further review.
Discussion. We have said previously that a warrant is not required to search an automobile “when police have probable cause to believe that a motor vehicle on a public way contains contraband or evidence of a crime, and exigent circumstances make obtaining a warrant impracticable.” Commonwealth v. Cast, 407 Mass. 891, 901 (1990). The United States Supreme Court later eliminated any requirement that exigent circumstances exist beyond the automobile’s “ready mobility,” and held that, “[i]f a car is readily mobile and probable cause exists to believe it contains contraband, the Fourth Amendment [to the United States Constitution] thus permits police to search the vehicle without more.” See Pennsylvania v. Labron, 518 U.S. 938, 940 (1996). The Court noted “that an individual has a lesser expectation of privacy in an automobile” because of its extensive regulation. Commonwealth v. Motta, 424 Mass. 117, 123 (1997), citing Pennsylvania v. Labron, supra. We subsequently concluded that “when an automobile is stopped in a public place with probable cause, no more exigent circumstances are required by art. 14 beyond the inherent mobility of an automobile itself to justify a warrantless search of the vehicle.” Id. at 124. We adopted the mobility rule of the Supreme Court for substantially the reasons discussed by the Court, observing that while art. 14 at times provides more protection than the Fourth Amendment, we had followed the Supreme Court in the area of the automobile exception on other occasions, and no compelling reason had been advanced to cause *558art. 14 and the Fourth Amendment to diverge in this area. See id. at 123-124.
Here, we are asked to consider whether, despite the inherent mobility rule, art. 14 requires the police to obtain a warrant before searching a vehicle when they have probable cause early enough to do so. The defendant does not challenge the inherent mobility rule; he contends, however, that once the police had probable cause, they delayed execution of the search here in a deliberate attempt to make use of the automobile exception in order to thwart the requirement of obtaining a warrant. The defendant argues that, in these circumstances, where the police had obtained evidence that provided a “plain and ample” opportunity to seek a search warrant prior to a search, art. 14 required them to do so despite the automobile exception. The defendant contends that here the decision to delay obtaining a warrant in order to gather additional evidence against the buyer was impermissible.3
The defendant does not dispute the evidence of probable cause in this case. To the contrary, he contends that, based on the inmate’s statement, there was probable cause to arrest the defendant on the afternoon of January 6, 2005, as well as throughout the day on January 7, 2005. It is for this reason that the defendant argues that the police had adequate time to obtain a search warrant before the stop on January 7, 2005, and were required to do so. The defendant claims that, as Foley testified, the police intended to arrest him on January 7, 2005, regardless of whether he entered his vehicle, and that the exigent circumstances purportedly justifying relaxation of the warrant requirement were created by the police decision to forgo the opportunity to obtain a search warrant for the vehicle earlier in the day.
As we have indicated, ordinarily additional exigent circumstances are not required when the search is of an automobile. We agree, however, that the automobile exception may not be employed to justify an unreasonable delay between the time *559when the police objectively have probable cause to search the car and the time when they do so. Commonwealth v. Motta, supra at 125. Once probable cause was established, the warrantless search of the defendant’s vehicle in the public parking lot was permissible; the question then becomes whether the police delayed execution of the search for an unreasonably long time without plausible justification for the delay. The time between an objective determination of probable cause and the conducting of the search of the automobile may be unreasonable, see Commonwealth v. Agosto, 428 Mass. 31, 34 (1998), if the police as an objective matter have no reasonable basis to expect that delay would produce any additional benefit. On the other hand, a reasonable period to further the investigation may be permissible to corroborate information received; because of an expectation that additional evidence will subsequently be located in the automobile; or in anticipation that the suspect or another will commit additional criminal acts. Once plain and ample opportunity to obtain a warrant is available, see Commonwealth v. Cast, supra at 904, quoting Commonwealth v. Bongarzone, 390 Mass. 326, 351 (1983), the police are nevertheless entitled to forgo application for the warrant if it is reasonable to do so and later to proceed with the search under the automobile exception.
The concurring justice characterizes our analysis as “reanimat[ing]” the abandoned “plain and ample opportunity” test, see Commonwealth v. Bongarzone, 390 Mass, at 350-351 (suggesting but not deciding that such a requirement might exist), as part of a “ ‘reasonable basis’ test.” Post at 564. That proposition conflates two separate considerations and thus misses the point. We agree that the existence of a plain and ample opportunity to obtain a warrant does not by itself require the obtaining of a warrant where a “readily mobile” vehicle is involved. See Pennsylvania v. Labron, 518 U.S. 938, 940 (1996). Indeed, in these types of cases, there will always be a plain and ample opportunity because, if such an opportunity does not exist, there would be probable cause coupled with exigent circumstances, and reliance on the automobile exception would be unnecessary.
Thus, a requirement that there be a “reasonable basis” for delay in executing a seizure following the advent of probable cause does not replicate “plain and ample opportunity,” because, *560by definition, there will already have been a plain and ample opportunity to obtain a warrant. What “reasonable basis” analysis does is move to a second, and entirely separate, inquiry, i.e., whether a delay in executing a permissible seizure is motivated by reasonable investigative considerations or merely by a desire to avoid the warrant requirement by exploiting the automobile exception. Given the significance of the warrant requirement in our constitutional framework, we consider this slight restriction on the exception a logical one.4
In the circumstances here, the police decision to delay the search in order to obtain corroborating evidence and to obtain sufficient evidence to arrest a second suspect was not so unreasonably long as to render the search invalid, and the police had an objective, defensible reason to justify waiting. The police were acting on tips from an inmate not necessarily reliable; it was not unreasonable to wait to see if the defendant was about to enter into the predicted transaction. See Commonwealth v. King, 35 Mass. App. Ct. 221, 226 (1993) (police entitled to wait until “last piece of probable cause had fallen into place”). Additionally, by waiting to see if the sale occurred, the police would have an opportunity to arrest a second individual, already known to them as a major drug dealer.
The defendant’s reliance on Commonwealth v. Agosto, supra at 34, is misplaced. In that case, the police seized a vehicle and held it for twenty-one days; they conducted several warrantless searches during that period before discovering heroin hidden in the vehicle. Id. at 32-33, 35. We concluded that the vehicle, because it was held in a police facility, was no longer mobile and that, therefore, the automobile exception did not apply. Id. at 34-35. We emphasized that, while broad, the automobile exception did not “giv[e] the police carte blanche to search without a warrant any time subsequent to a valid stop,” and that an “unreasonable delay . . . will render invalid an otherwise valid *561search.” Id. at 34, quoting Commonwealth v. Markou, 391 Mass. 27, 30 (1984), and Commonwealth v. Motta, supra at 125. In contrast, the search in the present case was conducted within minutes of the stop, while the vehicle was in the public parking lot; thus, there was no unreasonable delay following the seizure that would have rendered the vehicle immobile and made the automobile exception inapplicable.
The defendant’s reliance on Commonwealth v. Sergienko, 399 Mass. 291, 297 (1987), is also unavailing. In that case, we held that a delay of four and one-half hours between the observation of a marijuana cigarette in a defendant’s car, parked in his employer’s parking lot, and a warrantless search was unreasonable because the police had had sufficient time to obtain a warrant. In those circumstances, the delay was objectively unreasonable because it could not have enabled the police to corroborate information or obtain additional evidence: the marijuana cigarette was in plain view, and there was no indication that other suspects were involved or that further investigation would be fruitful.
Despite the defendant’s assertion to the contrary, Foley’s statements that he intended to arrest the defendant on the afternoon of January 7, 2005, regardless of whether the defendant entered his vehicle, and that he did not obtain a search warrant because he planned to rely on the automobile exception, do not invalidate the warrantless search. Foley also testified at the suppression hearing that he waited to see if the sale took place so that there would be sufficient evidence to arrest both men, and that an arrest of both men would have been preferable. If indeed these factors are present, delay is justified. However, a police officer’s motives are not material, because the determination of probable cause is an objective one. See Commonwealth v. Washington, 449 Mass. 476, 485-486 (2007).
In the circumstances here, although the police had ample opportunity to obtain a search warrant, the delay in conducting the search was objectively reasonable. Thus, a warrantless search of the automobile parked in a public place was permissible.
Judgments affirmed.
Five confidential informants and two named informants supplied information to the task force. The defendant does not dispute that a number of these informants were well-known to the police, had provided reliable information in the past, and met the requirements for reliability necessary to comport with art. 14 of the Massachusetts Declaration of Rights. See, e.g., Commonwealth v. Robinson, 403 Mass. 163, 164-165 (1988) (two-prong test of veracity and basis of knowledge necessary to establish probable cause under art. 14).
The tire store was located at the intersection of two major streets.
The defendant argued in his motion to suppress that the parking lot was not a public place; he did not pursue that argument before us, and we assume he has conceded the point. In addition, as the motion judge found, the public had access to the parking lot, see Commonwealth v. Gajka, 425 Mass. 751, 752 (1997) (“vehicle was parked in a public place and was apparently capable of being moved”), and this finding is warranted.
The alarm expressed by the concurring justice that our demand that there be a reasonable investigative basis for delay will embroil judges in more litigation, post at 562, is curious and misplaced. Both the Fourth Amendment to the United States Constitution and art. 14 require that searches not be unreasonable, and we have for some time expected that it is judges who will make the ultimate decisions on such issues. See Marbury v. Madison, 5 U.S. (1 Cranch) 137, 176-177 (1803).