The invasion of Iraq may be occurring on the other side of the globe, but the effects will be felt by travelers everywhere, from the corner gas station to the local airport.

Short of hiding in our homes for the duration, any journey is going to reacquaint Americans with the renewed realities of heightened security and uncertainty. Navigating travel in wartime will take extra preparation and patience. It’s the price for some kind of peace of mind.

“I think America wants us to be prepared — America wants us to take precautionary measures,” said Thomas Ridge, secretary of Homeland Security, on March 17, the day President Bush issued his ultimatum to Saddam Hussein to leave Iraq or face attack.

Ridge has even given the heightened domestic security measures one of those names usually reserved for military campaigns: Operation Liberty Shield.

Getting informed

Travelers should start by getting a general security assessment at the Department of Homeland Security, on the Web at www.whitehouse.gov/homeland/.

The home page for the command center in the nation’s war on terrorism, it has the latest updates on the color-coded security levels.

Even the lowest levels mean scrutiny at airports, but the Elevated (Orange) level — the current status — can lead to tighter border controls, limits to airport and other transportation-center access, and long delays at security checkpoints. A Severe (Red) level could mean the partial or complete shutdown of airports and borders, or at least extremely long delays at security checkpoints.

On the road

For many Americans who still want to travel during wartime, the answer is to hit the road and stay close to home. Automobile travel is on the upswing again, along with recreational vehicle use.

The main effect for road travelers will be the high cost of gasoline, which is well more than $2 a gallon throughout much of the country and is higher in some areas, such as Southern California. Some analysts expect a fuel-price spike during the war. Adding to the war is the unsettled situation in Venezuela, where ongoing civil unrest has strangled the flow of oil to the United States.

However, there is little chance of a fuel shortage of the kind Americans went through in the 1970s. Saudi Arabia has promised to open up a 50-million-barrel strategic reserve. The United States could also open its own strategic supplies if the price spiral continues. The question will be whether gasoline companies and gas-station owners pass along their savings to motorists.

To monitor the price of gasoline, check out the Web site www.fuelgaugereport.com. Also check out the Web sites of state auto clubs. Monitor what is going on at the Organization of Petroleum Exporting Countries Web site, www.opec.org.

National and state parks are reporting high volume of reservations for the spring and summer vacation periods. Check updates at www.nps.gov.

Domestic air travel

The biggest effect will be on the flying public. With the heightened security levels, airports are instituting new security procedures, which get tighter as the color-coded threat levels increase.

During Orange (Elevated) alerts, airport access can be limited and some roads shut down.

Red (severe) alerts could mean the partial or complete closing of some airports.

Most airports suggest arriving two hours before a domestic flight. Try to use public transportation because of increased inspections of private automobiles on the access roads and in the parking lots at airports. Restrictions on carry-on items are still in place and will likely be tightly enforced during the higher threat-alert levels.

In response to passenger concerns, many airlines have instituted temporary waivers of limits on the lowest-priced nonrefundable tickets. Some airlines offer one-time rebooking during specific times, while others link their looser policies to whether the government issues a Red alert.

Because there is no common policy between airlines and even differences in rules on the type of ticket at the same airline, learn the rules for your specific fare.

An added concern for travelers is that the war could push already teetering airlines over the brink. After the terrorist attacks of Sept. 11, 2001, airlines slashed the number of flights by 20 percent.

Cuts could occur if the war is prolonged or the rebound in travel immediately after is not speedy. Check well in advance to make sure airlines have not changed or canceled your flight.

For the current status of air travel in the United States, go to www.faa.gov. A list of what you can and cannot bring aboard a commercial airline flight can be found at www.tsa.gov.

Foreign travel

Traveling overseas during the war is cause for both trepidation and opportunity. Consult the long list of countries where the U.S. State Department says Americans should either not travel or are not recommended to visit on the Web at www.state.gov.

Travelers flying overseas are cautioned to arrive three hours before their flights and to be prepared for long lines and multiple security checkpoints. Limit the amount of carry-on luggage in order to speed time through the lines.

Make sure your passport is valid — some countries require at least six months of validity left before your next renewal date. Everyone — even infants — must have his or her own passport. Because of heightened security, the application process is taking longer. It takes at least six weeks for normal service and two weeks for expedited service. For information, go to travel.state.gov/passport_services.html.

The only upside of the conflict is that airlines are seeing a steep decline in the number of passengers. As a result, fares are at a 10-year low in some cases — as low as the Gulf War in 1991 — and airlines are waiving many cancellation and rebooking restrictions. If you can stomach the stress, you can take advantage — travel overseas hasn’t been this cheap in years.

For the best bargains, go to airline Web sites and sign up for weekly updates on sale fares. Travel services Web sites like www.travelocity.com also allow you to enter a limited number of destinations and will send you e-mails when fares drop by more than 1 percent.

Cruises

Some cruise lines are canceling voyages during the war. Others are loosening the refund and rebooking rules for passengers who feel uncomfortable about going to sea during the war. There is no industrywide standard, so contact individual cruise lines for more information. A good clearinghouse for information is the Cruise Lines International Assn. trade group, whose Web site is www.cruising.org.

Railroads

Amtrak does not plan any changes in service because of war. For passengers who have not taken the train in the past year, be aware that new security restrictions limit carry-on luggage to two bags per passenger (not including personal items such as laptops or purses). All baggage must be tagged with the name and address of the passenger. Information: www.amtrak.com.

Anti-Americanism abroad

Whatever your position on the war, you are an American. Many travelers fear they will be treated coolly even in countries like Britain — where the government supports the war, but polls show most people do not. France in particular has been a source of some worry for foreign travelers. The U.S. State Department cautions Americans traveling abroad not to call undue attention to themselves and to stay away from any public demonstrations.