This appeal involves the constitutionality of a vehicle checkpoint. Winfred Maxwell, a retired New York City police officer, brought this action against the city of New York and various police officials and officers for alleged violations of his constitutional and civil rights, under 42 U.S.C. §§ 1983, 1985(3), and 1986, and for corresponding violations of state law. Maxwell’s twenty-eight count amended complaint alleges, inter alia, that in going to visit his daughter, he was stopped by police at a barricaded vehicle checkpoint. He claims that , the existence of the checkpoint and resultant stop violated his Fourth Amendment right to be free from unreasonable searches and seizures. Maxwell further alleges that various police officers at the checkpoint used excessive force against him and illegally arrested, detained, and prosecuted him.
Appellants, Police Commissioner William Bratton, Lieutenant Thomas Kelly, Inspector Philip Lee, and Chief Thomas Gallagher, were responsible only for planning and ordering the establishment of the checkpoint. They were denied qualified immunity by Judge Mukasey on Maxwell’s claim for monetary damages for alleged Fourth Amendment violations in ordering the checkpoint. We hold that establishing the particular vehicle checkpoint without more did not violate Maxwell’s Fourth Amendment rights and reverse.
BACKGROUND
During the spring and summer of 1992, street crime, including four drive-by shoot*666ings, escalated in the Soundview neighborhood of the Bronx. In response, the 43rd precinct instituted the so-called Watson Avenue Special Operation. This involved a temporary vehicular checkpoint in an eight square-block narcotics-ridden area where most of the drive-by shootings had taken place. The checkpoint was to be active three days a week on a random, basis and for approximately six hours a day, primarily in the evening hours. When the checkpoint was in operation, officers manning the barricade were to stop every vehicle seeking to enter the area in order to ascertain the driver’s connection to the neighborhood. Drivers who approached the checkpoint were to be allowed to avoid questioning by driving around the area or by parking their cars and entering the area on foot. Area residents and commercial vehicles were to be allowed into the neighborhood. Officers manning the barricades were verbally instructed that they could also allow cars dropping off small children or visiting the local church to enter the area. Other than that, vehicles were not permitted beyond the barricades. The operation was in effect for six weeks, between August 26 and October 10,1992.
In the early evening .of September 19, 1992, Maxwell sought to drive to his daughter’s house, which was in the barricaded area.1 At the checkpoint Maxwell was directed by Officer Timothy Morley to stop the vehicle and to produce his driver’s license and registration. Maxwell alleges that he informed Morley that he was a retired police officer and that the pouch in which he kept his license and registration also contained a registered handgun. He then reached for the pouch and opened it. Upon observing the firearm, Morley drew his service revolver and. ordered Maxwell out of the vehicle. Maxwell alleges that he complied but that Morley nevertheless flipped him to the ground and made “unlawful physical contact” with him. A squad car of back-up officers soon arrived. Maxwell alleges that the officers unlawfully beat him, kicked him, punched him, and stepped on his neck. Thereafter, the officers handcuffed Maxwell and took him into custody. Maxwell claims that at this point he turned to one of the officers and said, “Sarge, look in the bag, I’m a retired police officer.” To which the officer allegedly replied, “I don’t care. As far as I’m concerned you’re a Nigger Dirtbag.” Maxwell was then taken by the officers to a station house where he was charged with Assault in the Second Degree, Resisting Arrest, Disorderly Conduct, and Harassment. He was detained until his arraignment the following day after which he was released. A jury acquitted Maxwell on all charges.
Maxwell filed the instant action alleging violations of his civil and constitutional rights as well as various state law claims. The district court granted the defendants’ motion for partial summary judgment with respect to various claims but declined to dismiss Maxwell’s Fourth Amendment claim for monetary damages for being stopped — apart from being arrested and beaten—at the checkpoint. Maxwell’s excessive force, illegal detention, and certain other claims were not the subject of the summary judgment motion and remain pending.
The district court also denied appellants’ motion that the complaint be dismissed as to Bratton, Kelly, Lee, and Gallagher on the ground of qualified immunity. They were of course involved only in planning and ordering the checkpoint and not in the arrest and alleged beating of Maxwell. In denying the motion, Judge Mukasey stated that “Because [Maxwell’s claim for monetary damages based on alleged Fourth Amendment violations] must proceed to trial, it cannot be determined at this stage whether plaintiff suffered any violation of his constitutional rights. Further, if plaintiffs version of the facts proves true, and the officers did not provide adequate instructions on how to operate the checkpoints, qualified immunity will not protect them.” Therefore, the court held that summary judgment was inappropriate and that the issue of qualified immunity must *667proceed to trial. This interlocutory appeal followed.
DISCUSSION
Only the district court's denial of the qualffied immunity defense as to the four appellants is before us. We review a district court's denial of summary judgment de novo. Aslanidis v. United States Lines, Inc., 7 F.3d 1067, 1072 (2d Cir.1993).
The district court denied qualified immunity in the belief that genuine questions of material fact exist as to whether the vehicle checkpoint itself-in contrast to the alleged misconduct of the officers manning the checkpoint-violated Maxwell's constitutional rights. Appellants are entitled to qualified immunity if either the checkpoint in question did not violate clearly established federal rights, see Harlow v. Fitzgerald 457 U.S. 800, 818, 102 S.Ct. 2727, 2736, 73 L.Ed.2d 396 (1982), or it was objectively reasonable for defendants to believe their conduct was lawful, see Anderson v. Creighton, 483 U.S. 635, 641, 107 S.Ct. 3034, 3039-40, 97 L.Ed.2d 523 (1987). The threshold inquiry is, of course, whether the plaintiff has alleged a constitutional violation at all. See Siegert v. Gilley, 500 U.S. 226, 232, 111 SCt. 1789, 1793, 114 L.Ed.2d 277 (1991); Blue v. Koren, 72 F.3d 1075 (2d Cir.1995).
In Michigan Department of State Police `a. Sits, the Supreme Court held that a Fourth Amendment "`seizure' occurs when a vehicle is stopped at a checkpoint." 496 U.S. 444, 450, 110 S.Ct. 2481, 2485, 110 L.Ed.2d 412 (1990); see also People v. Scott, 63 N.Y.2d 518, 524, 473 N.E.2d 1, 483 N.Y.S.2d 649 (1984) ("There is ... no question that a roadblock or checkpoint is a seizure within the meaning of the Fourth Amendment.") The reasonableness of a seizure at a vehicle checkpoint depends upon a balancing of (1) the gravity of the public concerns served by the checkpoint; (ii) the degree to which the checkpoint effectively addresses those concerns; and (iii) the severity of the intrusion upon individual liberty. Sitz, 496 U.S. at 448-49, 110 S.Ct. at 2484-85 (citing Brown v. Texas, 443 U.S. 47, 50-51, 99 S.Ct. 2637, 2640-41, 61 L.Ed.2d 357 (1979)). We con-elude that, as planned, the Special Operation passed constitutional muster.
First, the checkpoints in question served an important public concern in attempting to deter drive-by shootings that were, or were reasonably perceived to have been, connected with widespread drive-up drug purchases. Second, at the time of implementation, the checkpoints were reasonably viewed as an effective mechanism to deter criminal behavior in the barricaded area. Indeed, checkpoints similar to the one here had been effectively used in the past by the New York City Police. See Sitz, 496 U.S. at 453-54, 110 S.Ct. at 2486-87 (in order to satisfy the effectiveness prong, a checkpoint need only be one reasonable method of deterring the prohibited conduct; it need not be the most effective measure).
Third, the intended level of intrusion to motorists was minimal. No vehicle was to be stopped or its operation questioned unless entry into the cordoned-off area was desired. For those seeking entry, the stop was meant to be brief and was aimed solely at ascertaining the motorists' connection to the neighborhood. In United States v. Martinez-Fuerte, 428 U.S. 543, 96 S.Ct. 3074, 49 L.Ed.2d 1116 (1976), the Supreme Court held that a checkpoint aimed at interdicting the flow of illegal aliens which involved "only a brief detention Of travelers during which all that [was] required of the vehicle's occupants [was] a response to a brief question or two and possibly the production of a document evidencing a right to be in the United States" was not sufficiently intrusive so as to violate the Fourth Amendment: Id. at 558, 96 S.Ct. at 3083 (internal quotation marks omitted). Here, as in Martinez-Fuerte, the request for evidence of a legitimate reason to enter the barricaded area was not significantly intrusive. Moreover, because the plan here was to stop all motorists seeking entry, there was little concern that the stop would generate "fear and surprise." Sitz, 496 U.S. at 452-53, 110 S.Ct. at 2486-87; Martinez-Fuerte, 428 U.S. at 558, 96 S.Ct. at 3083 (where motorist can see that other vehicles are being stopped and can see visible signs of the officers' authority, there is less likelihood of fright or annoyance).
*668Maxwell next argues that even if stopping those who wanted to enter the Soundview area was valid, the plan empowered the officers with excessive discretion to turn people away and was therefore sufficiently intrusive to constitute a Fourth Amendment violation. In that regard, Maxwell cites the testimony of one sergeant that the decision to permit or forbid an individual vehicle’s entry “just comes down to the officer’s preference.” However, the instructions given allowed all residents and commercial vehicles to enter, as well as persons dropping off little children or visiting the church. It is true that discretion was to govern the inevitable myriad of other circumstances that might arise, but we know of no way to catalogue each of those circumstances in advance and to provide a litmus test to resolve them. We believe that the instructions were as detailed as was reasonably possible and, therefore, were constitutionally adequate.2
We emphasize the discretion afforded went only to the decision to permit or deny vehicular entry into the area, not to the detention of persons in the vehicles. Police roadblocks need not be based on reasonable suspicion of particular drivers, see Martinez-Fuerte, 428 U.S. at 556, 559-60, 96 S.Ct. at 3082, 3083-84, but the detention of particular motorists beyond the initial stop “may require satisfaction of an individualized suspicion standard.” Sitz, 496 U.S. at 451, 110 S.Ct. at 2485; see also Martinez-Fuerte, 428 U.S. at 566-67, 96 S.Ct. at 3087 (“The principal protection of Fourth Amendment rights at checkpoints lies in appropriate limitations on the scope of the stop.”) Thus, once the initial stop has been conducted, the decision to further detain a motorist must be based on particularized reasonable suspicion. See Terry v. Ohio, 392 U.S. 1, 27, 88 S.Ct. 1868, 1883, 20 L.Ed.2d 889 (1968); United States v. Sokolow, 490 U.S. 1, 7, 109 S.Ct. 1581, 1585, 104 L.Ed.2d 1 (1989). Our decision does not, therefore, affect Maxwell’s claims regarding events after the initial stop.
We conclude that summary judgment should have been granted as to the four appellants and reverse.
. Maxwell claims that, prior to arriving at the checkpoint, he observed no posted markings alerting him that he was approaching such a barricade and had no opportunity to avoid being stopped and questioned. Whether a failure to allow drivers to avoid the checkpoint might violate a driver's rights is not before us because Maxwell wanted to enter the area by car.
. We also note that simply turning away a vehicle when no legitimate reason for entry is given may not constitute a search or a seizure for Fourth Amendment purposes. In order for there to have been a “search,” “the police must have physically intruded into 'a constitutionally protected area.'" See 1 LaFave, Search & Seizure § 2.1(a), at 302-03 (2d ed. 1987). Refusing entrance does not intrude into any such area. Similarly, a "seizure” requires that an officer restrict the liberty of an individual such that a reasonable person would not believe that he was free to leave. Id. (citing United States v. Mendenhall, 446 U.S. 544, 100 S.Ct. 1870, 64 L.Ed.2d 497 (1980)). In Sheppard v. Beerman, 18 F.3d 147 (2d Cir.), cert. denied, - U.S. -, 115 S.Ct. 73, 130 L.Ed.2d 28 (1994), we held that no Fourth Amendment "seizure” took place when a fired court employee was escorted from the courthouse. We reasoned that because the plaintiff was free to go anywhere in the world, except the courthouse, he had not been "seized.” Id. at 153. Here, the plan was that motorists who were denied entry for lack of any legitimate reason to go into the area were free to go anywhere else.