McHUGH, J.

After a State police officer noticed an inoperable headlight on the car driven by the defendant, Kenton Feyenord, the officer stopped the car. Soon after the stop, the officer found 169 grams of cocaine concealed in the trunk. Before his trial on resulting charges of trafficking in cocaine (G.L. c. 94C, § 32E[ b][3]), the defendant, invoking both the Fourth Amendment to the Constitution of the United States and art. 14 of the Massachusetts Declaration of Rights, filed a motion to suppress all physical evidence taken from the vehicle and all statements made to the officer prior to the search. His motion was denied. The defendant was subsequently convicted of trafficking cocaine, in the amount of one hundred to two hundred grams, on a joint venture theory. Now he appeals, claiming that the denial was error. We affirm.

The events relevant to the motion to suppress began when State police officer William Pinkes, while on patrol at 5:45 P.M. on May 4, 2000, noticed a car behind him with its right headlight illuminated and its left headlight out. It was daylight at the time and there were no visibility hazards. As some motorists are wont to do, however, the driver had turned on the headlights prior to nightfall.

Pinkes pulled his marked cruiser to the side of the road and allowed the vehicle to pass him. After the car passed, he pulled behind it, and signaled the driver to stop. As Pinkes walked toward the stopped vehicle, he saw the defendant, a bearded black man, seated behind the wheel and a passenger, subsequently identified as "Junior" Cox, sans seat belt, sitting beside him.

Pinkes asked the defendant for his license and registration. The defendant was unable to produce a valid driver's license but did show Pinkes a proper vehicle registration certificate in the name of a person he claimed was his aunt. As the defendant produced the registration, Pinkes noticed that the defendant was nervous and that his hands were shaking. In response to Pinkes's request, Cox produced a valid identification card showing him to be a Jamaican citizen. When Pinkes asked the defendant for his name, however, the defendant's response was unintelligible.

Following the unintelligible response, Pinkes ordered the defendant to get out of the vehicle so he could question him apart from Cox, who remained inside the vehicle. The ensuing exchange between Pinkes and the defendant occurred while the two were standing between the front of Pinkes's cruiser and the rear of the defendant's car. Pinkes began the conversation by again asking the defendant for his name. This time, the defendant replied that his name was Kadari Bowen. He provided a social security number and a birth date of June 9, 1978, but stumbled when asked for his age. At some point, the defendant said he was licensed to drive in New York but, as noted, was unable to produce any driver's license.

Leaving the defendant between the two parked cars, Pinkes went to the driver's side of the defendant's car and asked Cox who the defendant was and how long Cox had known him. Cox replied that, although he had known the defendant for two to three years, he only knew him as "Pat."

Armed with that information, Pinkes returned to the defendant and asked him how long he had known Cox. The defendant stated that Cox was his brother-in-law, the father of his sister's child, and that the defendant had known him for approximately twelve years. At that, Pinkes returned to the side of the car and asked Cox for the name of the defendant's sister. Cox told Pinkes that he did not know any of the defendant's family.

Pinkes then inquired of the defendant about the pair's intended destination. The defendant said that he and Cox were on their way to Putnam, Connecticut, to visit one of the defendant's friends. Although he did not know the friend's address or telephone number, the defendant said he intended to telephone the friend for directions when he got a little closer to Putnam. Cox, on the other hand, told Pinkes that the pair was headed for Brooklyn, New York.

At that point, Pinkes decided that something meriting further investigation was afoot. He placed the defendant in the back of his cruiser while he contacted State police Officer James Devlin, who was assigned to the area as the handler of Heiko, a police dog trained to detect marijuana, cocaine, hashish, and heroin. Pinkes asked Devlin to come to the scene. Between five and ten minutes had elapsed between the stop and Pinkes's call to Devlin. The defendant was not handcuffed as he sat in the rear of Pinkes's cruiser and Pinkes informed him that he was not under arrest. Pinkes also told him, however, that he was not free to leave the cruiser.

Devlin and Heiko arrived at the scene ten or fifteen minutes after Devlin received Pinkes's call. After arriving, Devlin had Heiko walk around the exterior of the defendant's vehicle. Heiko "alerted" in an area at the left rear of the trunk. The officers then placed Heiko near the inside of the trunk, where he again "alerted," this time in an area near the left rear tail light. Upon inspection, the police officers found a gray plastic bag containing a digital scale and a black bag holding a quantity of what looked like, and turned out to be, cocaine. At that point, the defendant and his passenger were arrested and brought to the State police barracks.

Based on those facts, the defendant makes three related arguments attacking the validity of the search. First, he contends that Pinkes was not authorized to stop him for operating the car during daylight hours with only one functioning headlight. Second, he claims that Pinkes did not have a lawful basis for ordering him to get out of the vehicle. Finally, the defendant claims that his detention at the scene and the dog's exterior sniffing of his car amounted to an impermissible search, seizure, or both.

1. The stop. The motion judge determined that operating a motor vehicle with only one headlight, during the daytime, was a traffic violation and warranted the stop. The defendant argues that there was no traffic violation. He focuses on G.L. c. 90, § 7, which, among other things, requires that headlamps be illuminated from one-half hour after sunset to one-half hour before sunrise. He concedes that headlamps must be illuminated if weather conditions during daylight hours create a visibility hazard. Absent this circumstance, however, his position is that no traffic offense had occurred and no stop was justified.

The defendant's argument is unpersuasive. General Laws c. 90, § 7, states that "[e]very motor vehicle operated in or upon any way shall be provided with . . . suitable lamps." G.L. c. 90, § 7, as appearing in St. 1978, c. 439, § 1. "Lamps" is in the plural and the requirement for "suitable lamps" depends neither on visibility conditions nor on the time of day during which the vehicle is operated.

The statute does not define the word "suitable." However, the sentence immediately after the sentence containing the "suitable lamps" requirement says that:

"[e]very automobile operated during the period from one half an hour after sunset to one half an hour before sunrise, and during any other period when visibility is reduced by atmospheric conditions so as to render dangerous further operation without lights being displayed, shall display at least two lighted white headlamps with at least one mounted at each side of the front of the vehicle."

G.L. c. 90, § 7, as appearing in St. 1978, c. 439, § 1. See G.L. c. 90, § 7A (requiring annual inspection to insure that, inter alia, "lights" are in good working order); 540 Code Mass. Regs. § 22.05 (1996) (specifying the number of feet in front of vehicle lamps must be capable of illuminating). When the statutory provisions are "construed together so as to constitute a harmonious whole consistent with the legislative purpose," Board of Educ. v. Assessor of Worcester, 368 Mass. 511, 513-514 (1975), we think that, at a minimum, the "suitable" lamps with which vehicles must be equipped are lamps capable of meeting the statutory requirements for illumination at night and during periods of reduced visibility, i.e., "two lighted white headlamps with at least one mounted at each side of the front of the vehicle." See G.L. c. 90, § 7. Lamps capable of being lighted manifestly must be in operating order and one of the lamps on the defendant's car was not. Therefore, the defendant's vehicle was not "provided with" "suitable" lamps and Pinkes was authorized to stop it. See, e.g., Commonwealth v. Riche, 50 Mass. App. Ct. 830, 833 (2001).

2. The exit order. When Pinkes stopped the defendant's car, Pinkes knew only that it was not properly equipped for travel on the Commonwealth's roads. Because the stop was justified, however, he was permitted to "take reasonable precautions for [his] own protection." "Such precautions may include ordering occupants out of a car for questioning," Commonwealth v. Ferrara, 376 Mass. 502, 505 (1978), if the officer who makes the stop has reasonable concern for his own safety or that of others. See Commonwealth v. Gonsalves, 429 Mass. 658, 660-669 (1999), S.C., 432 Mass. 613 (2000), S.C., 441 Mass. 1007 (2004). Given the wide variety of rapidly evolving circumstances an officer may face, "not . . . much [is required] for a police officer to establish a reasonable basis to justify an exit order . . . based on safety concerns." Id. at 664.

Here, Pinkes was justified in ordering the defendant out of the car when he failed to produce a valid driver's license and produced a registration certificate in the name of another. Those circumstances, combined with the defendant's nervous mannerisms, suggested, at the very least, that "something was amiss," Commonwealth v. Heon, 44 Mass. App. Ct. 254, 257 (1998), and gave rise to "a suspicion of other offenses, such as automobile theft." Commonwealth v. Lantigua, 38 Mass. App. Ct. 526, 528 (1995). Particularly because Pinkes was alone and outnumbered, the circumstances "reasonably [gave] rise to . . . and justifie[d] [Pinkes's] heightened precautions for [his] own safety." Ibid. See Commonwealth v. Kitchings, 40 Mass. App. Ct. 591, 596-597 (1996); Commonwealth v. Riche, supra at 834. In sum, the exit order was permissible.

3. The exterior sniff of the vehicle. The final question is whether the exterior sniff of the vehicle was improper either because Pinkes impermissibly extended the length of time he was holding the defendant at the scene awaiting the dog's arrival, or because the dog's sniff amounted to an impermissible search of the defendant's automobile without probable cause.

We deal first with the issue of whether the sniff was a search. If so, Pinkes required either a warrant or probable cause and an exception to the warrant requirement. United States v. Place, 462 U.S. 696, 706-707 (1983). However, insofar as the Fourth Amendment to the Constitution of the United States is concerned, the sniff was not a search. Id. at 707. See Indianapolis v. Edmond, 531 U.S. 32, 40 (2000); Commonwealth v. Sinforoso, 434 Mass. at 324; Commonwealth v. Pinto, 45 Mass. App. Ct. 790, 793 (1998). And, although no decided case has thus far said so, we think the same result obtains under art. 14 of the Massachusetts Declaration of Rights.

"[W]hether a search in the constitutional sense has taken place . . . turns on whether the police conduct has intruded on a constitutionally protected reasonable expectation of privacy." Commonwealth v. Montanez, 410 Mass. 290, 301 (1991) (citation omitted). "[A] constitutionally protected reasonable expectation of privacy" has a subjective and an objective component. Ibid. The subjective element turns on "whether the defendant has manifested a subjective expectation of privacy in the object of the search," and the objective element turns on "whether society is willing to recognize that expectation as reasonable." Ibid. The defendant bears the burden of establishing both elements, ibid., and, on review, we treat the issue as a question of law. See Commonwealth v. Starr, 55 Mass. App. Ct. 590, 593 (2002).

Nothing in the record suggests that the defendant subjectively expected that the odors his automobile was emitting that evening, odors detectable only by a trained dog, were surrounded by a zone of privacy. By itself, that void is sufficient to defeat his claim that a search occurred. See, e.g., Commonwealth v. Ortega, 59 Mass. App. Ct. 217, 221-222 (2003), S.C., 441 Mass. 170 (2004).

But even if the defendant had such an expectation, the dog's activity did not amount to a search. From the mix of smells escaping the defendant's car, the dog was trained to "alert" only to the odor of marijuana, cocaine, hashish, and heroin. In other words, the presence or absence of the dog's visible reaction to what he smelled

"disclose[d] only the presence or absence of narcotics, a contraband item. Thus, despite the fact that the sniff tells the authorities something about the contents of the [automobile], the information obtained is limited. This limited disclosure also ensures that the owner of the property is not subjected to the embarrassment and inconvenience entailed in less discriminate and more intrusive investigative methods.

In these respects, the canine sniff is sui generis. We are aware of no other investigative procedure that is so limited both in the manner in which the information is obtained and in the content of the information revealed by the procedure."

United States v. Place, 462 U.S. at 707. Compare, e.g., Kyllo v. United States, 533 U.S. 27, 38-39 (2001).

Under the principles to which we have long adhered, therefore, the dog's sniff and resulting "alert" would constitute a search only if society were prepared to say that the defendant was reasonable in his subjective expectation of privacy in the odor of cocaine emanating from his car. We think that society is wholly unprepared and unwilling to take that step. See United States v. Morales-Zamora, 914 F.2d 200, 205 (10th Cir. 1990).

We recognize that there may be circumstances under which a canine sniff would constitute a search. "The question always to be asked is whether the use of a trained dog intrudes on a legitimate expectation of privacy." United States v. Thomas, 757 F.2d 1359, 1366 (2d Cir.), cert. denied sub nom. Fisher v. United States, 474 U.S. 819 (1985). For that reason, use of a dog to, say, sniff the body of a person raises issues very different from use of a dog to sniff luggage or the exterior of a car. The issues are different not because society is prepared to recognize an expectation of privacy in the odor of contraband concealed upon a person, as opposed to the odor of contraband concealed in a car, but because the very act of sniffing a person, and the touching that may accompany that sniffing, may be degradingly intrusive. See Horton v. Goose Creek Indep. Sch. Dist., 690 F.2d 470, 479 (5th Cir. 1982), cert. denied, 463 U.S. 1207 (1983); B.C. v. Plumas Unified Sch. Dist., 192 F.3d 1260, 1266 (9th Cir. 1999); United States v. Kelly, 302 F.3d 291, 293 n. 1 (5th Cir.), cert. denied, 537 U.S. 1094 (2002); Merrett v. Moore, 58 F.3d 1547, 1553 (11th Cir. 1995), cert. denied, 519 U.S. 812 (1996). At least one circuit court has concluded that a dog sniffing at the door of an apartment produces a similar intrusion. United States v. Thomas, supra at 1367. But even if canine drug detection in other settings is intrusive enough to constitute a search, that kind of intrusion simply is not present when a dog sniffs the exterior of an automobile. Consequently, sniffs of that kind are not searches under art. 14 any more than they are under the Fourth Amendment, and neither probable cause nor reasonable suspicion was required before bringing the dog to the scene.

Many of the cases dealing with dogs and their discovery of drugs secreted in automobiles and trucks, however, do not turn solely on the question whether the dog's investigation amounted to a search. Instead, the cases turn on the second question of impropriety the defendant raises, namely, whether the defendant's detention for the length of time required for a dog-assisted drug investigation following a routine traffic stop unreasonably and impermissibly extended the stop's scope. See Commonwealth v. Sinforoso, 434 Mass. at 325-326 n. 5. See also United States v. Quinn, 815 F.2d 153, 159-160 (1st Cir. 1987); United States v. Morales-Zamora, 914 F.2d at 202-203; United States v. Gregory, 302 F.3d 805, 809-810 (8th Cir. 2002), cert. denied, 538 U.S. 992 (2003); People v. Caballes, 207 Ill. 2d 504, 509 (2003), cert. granted, 541 U.S. 972 (2004); Bradshaw v. State, 759 N.E.2d 271, 273-274 (Ind.App. 2001); State v. Wiegand, 645 N.W.2d 125, 134-135 (Minn. 2002).

In one way or another, cases that undertake to examine the nexus between the purpose for which the stop was effected and the scope of the resulting detention and investigation typically use an analytical model drawn from the basic principle found in Terry v. Ohio, 392 U.S. 1 (1968). Our dissenting colleague does likewise. Under Terry, police officers who lack probable cause to make an arrest may nevertheless stop and detain a citizen if, and to the extent that, their action is justified at its inception and the police activity following the stop is reasonably related in scope to the circumstances that justified the stop in the first place. Id. at 19-20. Our own cases follow that model by requiring police officers to allow motorists they stop for routine motor vehicle infractions to proceed as soon as the officers have satisfied the purposes for which they effected the stop unless events occurring thereafter provide a basis for extending the stop's duration or increasing the investigation's scope. See Commonwealth v. Bacon, 381 Mass. 642, 644 (1980); Commonwealth v. King, 389 Mass. 233, 243-244 (1983); Commonwealth v. Crowley, 29 Mass. App. Ct. 1, 4-5 (1990).

In this case, however, the Terry model is inapplicable because there was probable cause to arrest the defendant before Pinkes summoned the dog. Pinkes's questioning revealed that the defendant held a New York driver's license but did not have that license in his possession. Upon making that discovery, Pinkes was authorized by G.L. c. 90, § 21, to arrest the defendant for violating G.L. c. 90, § 10, which, among other things, requires out-of-State drivers to have their licenses in their possession while driving on the roads of Massachusetts. See generally Commonwealth v. Lantigua, 38 Mass. App. Ct. at 528.

To be sure, Pinkes did not arrest the defendant for nonpossession of a license, choosing instead to hold him at the scene while he summoned the dog. The record does not tell us what Pinkes would have done if the dog had smelled nothing of interest. But no rule requires police to effect an arrest the moment they have probable cause to do so, see Commonwealth v. Celestino, 47 Mass. App. Ct. 916, 918 (1999); cf. Commonwealth v. Moscat, 49 Mass. App. Ct. 622, 624 (2000), nor does any rule suggest that police are prohibited from briefly detaining a person who they have probable cause to arrest while they decide whether to arrest the person or let her proceed. Arrest, of course, triggers a series of important, formalized procedural rights, see generally, e.g., Jenkins v. Chief Justice of the Dist. Ct. Dept., 416 Mass. 221, 232-238 (1993); Commonwealth v. Morse, 427 Mass. 117, 123 (1998), and police officers cannot use detention without arrest as a device for avoiding that trigger. But the approximately thirty-minute detention involved here displayed no effort to evade formality and it left open the possibility that, if the dog finished its investigation without incident, no arrest would follow. To hold that the defendant's detention was unlawful because the police did not arrest him before the investigation began would turn an arrest into a constitutional safeguard against brief detention. We have described that kind of result as "odious," see Commonwealth v. Skea, 18 Mass. App. Ct. 685, 694 (1984), for it creates incentives wholly inconsistent with the constitutional interests the rules governing detention without arrest are designed to serve.

In sum, Trooper Pinkes properly stopped the defendant for a traffic offense and asked him to get out of his vehicle. The police dog's subsequent sniffing of the air outside the defendant's car was not a search and the defendant's brief detention while the dog was summoned to the scene and conducted his inquiry did not amount to an impermissible seizure of the defendant. The judge, therefore, rightly denied his motion to suppress.

Judgment affirmed.